The FBI identified the 20-year-old Pennsylvania resident who was killed after trying to assassinate Trump as Thomas Matthew Crooks.

Crooks was a resident of Bethel Park, a village about 55 miles south of the shooting scene in Butler, Pennsylvania.

He was registered to vote as a Republican. But records show that his one known political donation, for $15 in 2021, was to Act Blue, a group that supports Democratic candidates.

Crooks was killed after firing several shots from a rooftop overlooking the rally site.

Crooks was not carrying identification at the time of the shooting. Investigators spent hours confirming his suspected identity.

- Dan Mangan

Ukraine's President Volodymyr Zelenskyy said on X early Sunday morning that he was "appalled" to hear about the shooting of former U.S. President Donald Trump.

"I am appalled to learn about the shooting of former U.S. President Donald Trump at his rally in Pennsylvania," he said in a post on X.

"I am relieved to learn that Donald Trump is now safe and wish him a speedy recovery," he added, also offering his condolences to the loved ones of the rally attendee who died.

"I extend my wishes for strength to everyone who is horrified by this event. I wish America emerges stronger from this," Zelenskyy said.

— Weizhen Tan

The Secret Service did not field a representative for a law-enforcement press conference on the shooting, leaving unanswered questions many reporters had about whether there were failures in securing the rally scene that became the site of an assassination attempt on Donald Trump.

Instead, Kevin Rojek, the FBI's top agent in Pittsburgh and the commissioner of the Pennsylvania State Police handled questions from the press, often saying they could not, or would not comment on the Secret Service's actions.

Questions were immediately raised about how the now-dead gunman was able to get on a roof, with a rifle, overlooking the rally where Trump was speaking, and how he was able to fire multiple shots, killing one man and critically injuring two others.

Rojek called the fact that the shooter could fire off those shots before being killed "surprising."

As a former president, Trump has lifetime Secret Service protection, and he would have it anyway as the Republican party's presumptive presidential nominee.

"They do the initial security assessments and determine where the different security locations should be," Rojek said. "And they're the ones who are in charge of securing the scene."

- Dan Mangan

An FBI agent said investigators have "no identified motive" in what authorities consider an "assassination attempt" on Trump.

Kevin Rojek, Special Agent in Charge of the FBI's Pittsburgh Field Office, said authorities are not prepared yet to release the name of the now-dead shooter, who has been tentatively identified.

"There was no identification on the individual," said Rojek, noting that investigators are checking the shooter's biometric information, DNA and photographs to confirm his identity.

Pennsylvania State Police Commissioner Col. Christopher Paris said, "We have no reason to believe there is any other existing threat out there."

- Dan Mangan

President Joe Biden's motorcade arrived at Dover Air Force Base in Delaware at 11:24 p.m. He is expected to arrive back at the White House around 12:30 a.m.

– Josephine Rozzelle

The man killed after shooting at Trump during the rally was about 20 years old and a resident of Pennsylvania, five senior U.S. law enforcement officials told NBC News.

- Dan Mangan

Former President Donald Trump has left the hospital where he was being treated, according to Pennsylvania Governor Josh Shapiro.

"Under the protection of US Secret Service and with the assistance of the Pennsylvania State Police, former President Trump has now left the Butler area," Shapiro said in a post on X. "Lori and I are thankful that his team reports that he is fine and we continue to wish him a full and speedy recovery."

– Josephine Rozzelle

Democrats began pushing back on suggestions by Trump to blame President Joe Biden and other members of their party for the apparent assassination attempt.

"It's extremely dangerous but sadly unsurprising," a Democratic operative told NBC News.

"The GOP will fan the flames of division that directly contributed to this violence, then blame Democrats for the raging fire that threatens to burn down the fabric of our democracy," the operative said.

"This is their playbook. We've reached a dark turning point in this race. I worry it will only get worse from here."

- Dan Mangan

The House of Representatives "will conduct a full investigation of the tragic events" at the Trump rally, Speaker Mike Johnson said.

"The American people deserve to know the truth," the Louisiana Republican said in a tweet.

"We will have Secret Service Director Kimberly Cheatle and other appropriate officials from [Department of Homeland Security] and the FBI appear for a hearing before our committees ASAP," Johnson wrote.

- Dan Mangan

President Joe Biden has spoken to former President Donald Trump following the campaign rally shooting in Pennsylvania, a White House official said.

Biden has also spoken with Pennsylvania Gov. Josh Shapiro and Bob Dandoy, the Mayor of Butler, Pennsylvania, the official told reporters.

The official offered no details about the calls.

Biden, who delivered remarks earlier Saturday evening condemning the "sick" act of apparent political violence, is set to receive an updated briefing at the White House on Sunday morning, the official said.

— Kevin Breuninger

Washington's Metropolitan Police Department is bolstering its security presence throughout the city in response to the Trump rally shooting.

"Out of an abundance of caution, MPD has increased police presence across the city," Police Chief Pamela Smith said in a statement.

Smith said there were no "known threats" to Washington but that the public should stay vigilant of suspicious activity.

The MPD provided several tip lines for reporting suspicious behavior: either call 202-727-9099, text 50411, or visit iwatchdc.org online.

— Rebecca Picciotto

Rep. Ronny Jackson, a Texas Republican who served as the White House's chief doctor for Trump and former President Barack Obama, told Fox News that his nephew's neck was grazed by a bullet during the shooting at Trump's rally.

"My nephew was at the event tonight, and they were in the friends and family pen, and they heard this shot and everybody dropped to the ground ... he was grazed in the neck, a bullet crossed his neck, cut his neck, and he was bleeding," Jackson told Fox's Sean Hannity.

The former Navy officer said his nephew, who he did not identify by name, said the relative was sitting to the Trump right during the incident, "in the line of fire and they heard shots coming in."

Jackson said there was someone who was four or five rows behind his nephew who was critically injured.

"My sister-in-law had encouraged him to go the ... first aid tent, to the triage tent," Jackson said.

"When they got to the triage tent while they were there was another member of the crowd and unfortunately was in the triage tent on a gurney ... that had a devastating wound, had a critical wound to the head and was dead," the congressman said.

Trump nominated Jackson as secretary for Veteran's Affairs in 2018, but Jackson dropped out as the nominee weeks later amid allegations about his professional conduct.

- Dan Mangan

The suspected shooter was positioned roughly 148 yards from the Trump rally stage, according to an NBC News map visualization of the shooting.

— Rebecca Picciotto

President Joe Biden is leaving Rehoboth Beach, Delaware and returning to the White House tonight, the White House said.

Biden had originally planned to be in Rehoboth Beach all weekend.

– Josephine Rozzelle

The FBI, which is leading the investigation of the shooting, urged anyone with information about the incident to call the bureau's tip line, 1-800-CALL-FBI."

"Special agents of the FBI Pittsburgh Field Office responded immediately [to the scene] to include crisis response team members and evidence response technicians," the FBI said in a statement.

"We will continue to support this investigation with the full resources of the FBI, alongside our partners at the U.S. Secret Service and state and local law enforcement."

- Dan Mangan

The New York Police Department is adding extra officers and resources to Trump Tower in Manhattan, which contains Trump's apartment, as a result of the shooting.

Trump Tower also houses business offices of the Trump Organization, the company owned by the former president.

At Trump's golf club in Bedminster, New Jersey, where he also maintains a residence, several police squad cars with lights flashing were guarding the club's entrance.

— Dan Mangan

EDITORS NOTE

GRAPHIC CONTENT: Images depict gunshot wounds and an image of the body of the dead suspected shooter.

A screen grab photo from a video shows the body of the suspected shooter at the Pennsylvania rally on a building roof that overlooked Trump's event.

The man was killed by the Secret Service after allegedly firing the shots in an apparent assassination attempt on Trump.

The building where the suspected shooter was killed was outside the security perimeter of the rally.

- Dan Mangan

A witness outside the Trump rally told the BBC that he noticed a man with a rifle "bear-crawling" up a building roof minutes before shots were fired.

"We're pointing at the guy crawling up the roof," Greg, the witness, said.

He added that he tried to flag the police down once he saw what was happening and stood pointing at the man on the roof for several minutes.

"Next thing you know, I'm thinking to myself, I'm like, 'Why is Trump still speaking? Why have they not pulled him off the stage?'" Greg told the BBC.

The shooting occurred outside of the Secret Service's security perimeter for the event, three senior U.S. law enforcement officials told NBC News.

— Rebecca Picciotto

Secretary of Homeland Security Alejandro Mayorkas said in a statement that he and U.S. Secret Service Director Kimberly Cheatle briefed President Joe Biden on the shooting.

"DHS and the Secret Service are working with law enforcement partners to respond to and investigate the shooting," Mayorkas said in the statement. "We condemn this violence in the strongest possible terms and commend the Secret Service for their swift action today.

"We are engaged with President Biden, former President Trump, and their campaigns, and are taking every possible measure to ensure their safety and security. Maintaining the security of the Presidential candidates and their campaign events is one of our Department's most vital priorities," he said.

– Josephine Rozzelle

Attorney General Merrick Garland said he has been briefed on the shooting at Trump's rally, and also has briefed President Joe Biden.

"The FBI, ATF, U.S. Attorney's Office for the Western District of Pennsylvania, and the Department's National Security Division are currently working with the Secret Service as well as state and local law enforcement partners on the ground in Butler, Pennsylvania," Garland said in a statement released by the Department of Justice.

"My heart is with the former President, those injured, and the family of the spectator killed in this horrific attack," Garland said. "We will not tolerate violence of any kind, and violence like this is an attack on our democracy. The Justice Department will bring every available resource to bear to this investigation."

- Dan Mangan

The shooting at Trump's campaign rally occurred less than two days before the highest-profile Republicans from across the country are set to convene for the party's nominating convention in Milwaukee.

The four-day event will largely take place at the Fiserv Forum, a nearly 20,000-capacity arena that is home to the Milwaukee Bucks basketball team.

It is unclear whether the Republican National Committee will increase security in light of the shooting and, if so, how the organizers will do so with little time to spare.

Asked for comment about those security plans, an RNC spokesman directed CNBC to a joint statement from the organization's chairs and the Trump campaign that included no mention of how the event will be secured.

"As was communicated earlier this evening, President Trump is doing well and grateful to law enforcement and first responders for their fast action," read the statement from top Trump campaign aides Susie Wiles and Chris LaCivita, as well as RNC chairman Michael Whatley and co-chair Lara Trump.

"President Trump looks forward to joining you all in Milwaukee as we proceed with our convention to nominate him to serve as the 47th President of the United States. As our party's nominee, President Trump will continue to share his vision to Make America Great Again," their statement read.

— Kevin Breuninger

The suspected shooter at the Trump rally is a male, four senior U.S. law enforcement officials briefed on the investigation told NBC.

– Josephine Rozzelle

Several of Donald Trump's loudest supporters have blamed President Biden's campaign rhetoric for the apparent assassination attempt on the former president.

"Today is not just some isolated incident. The central premise of the Biden campaign is that President Donald Trump is an authoritarian fascist who must be stopped at all costs," Sen. JD Vance, R-Ohio., a frontrunner to be Trump's vice presidential pick, said on X. "That rhetoric led directly to President Trump's attempted assassination."

Sen. Tim Scott, R-S.C., echoed that message, accusing Democrats of stoking political violence.

"For years, Democrats and their allies in the media have recklessly stoked fears, calling President Trump and other conservatives threats to democracy," he wrote. "Their inflammatory rhetoric puts lives at risk."

— Rebecca Picciotto

President Joe Biden drew criticism from conservatives for his comment on a call with donors earlier this week that "it's time to put Trump in the bullseye."

The official X social media account of the Republican caucus on the House Judiciary Committee tweeted Biden's quote, and noted, "That just happened."

"Defend that. Go ahead," tweeted Fox News contributor Joe Concha about the comment. "Try to defend that rhetoric after what we all just witnessed with Trump coming with a centimeter of being assassinated.

Biden said in the call Monday with donors, "I have one job, and that's to beat Donald Trump. I'm absolutely certain I'm the best person to be able to do that."

"So, we're done talking about the debate. It's time to put Trump in the bullseye," Biden said.

- Dan Mangan

Several Republican House committee leaders are calling for briefings and a congressional hearing with Secret Service members about the apparent assassination attempt on former President Donald Trump.

House Oversight Committee Chair James Comer, R-Ky., said he has contacted the Secret Service to schedule a briefing on the shooting and to set a congressional hearing with Secret Service Director Kimberly Cheatle.

"There are many questions and Americans demand answers," Comer said in a statement, adding that the committee will send a "formal invitation" to the Secret Service soon.

The Republican members of the House Homeland Security Committee also requested a Secret Service briefing for Saturday evening, according to their social media post.

— Rebecca Picciotto

Video cameras captured the moment when a shooter fired while former President Donald Trump was on stage at a campaign rally in Pennsylvania.

The footage shows Trump jolting in response to the shot — which he later said grazed his right ear —and then falling to the floor as Secret Service rushes around him.

— Kevin Breuninger

Photographers captured images of former President Donald Trump with thin streaks of blood on his face, as well as the chaos that followed.

The U.S. Secret Service released an new statement on the shooting at the Trump rally:

"During former President Trump's campaign rally in Butler, Pennsylvania on the evening of July 13th at approximately 6:15 p.m., a suspected shooter fired multiple shots toward the stage from an elevated position outside of the rally venue.

"US Secret Service personnel neutralized the shooter, who is now deceased. US Secret Service quickly responded with protective measures and the former president is safe and being evaluated. One spectator was killed, two spectators were critically injured.

"The incident is currently under investigation and the Secret Service has formally notified the Federal Bureau of Investigation."

– Josephine Rozzelle

Ivanka Trump, the former president's eldest daughter, in a social media post thanked those who have shared "love and prayers for my father and for the other victims of today's senseless violence in Butler, Pennsylvania."

"I continue to pray for our country," her post read. "I love you Dad, today and always."

— Kevin Breuninger

Several hours after the shooting, Donald Trump took to Truth Social to send condolences to the families of the members of the crowd who were killed and injured.

He also relayed his memory of the experience: "I was shot with a bullet that pierced the upper part of my right ear. I knew immediately that something was wrong in that I heard a whizzing sound, shots, and immediately felt the bullet ripping through the skin. Much bleeding took place, so I realized then what was happening."

He thanked the Secret Service and law enforcement officials who rapidly responded at the scene and reiterated that the shooter was dead, though he said he did not have further information.

"It is incredible that such an act can take place in our Country," Trump added.

— Rebecca Picciotto

The U.S. Secret Service has requested the FBI's assistance in investigating the shooting at former President Donald Trump's rally in Pennsylvania on Saturday.

"FBI personnel are on the scene in Butler, Pennsylvania and the FBI will continue to work jointly with the U.S. Secret Service as the investigation moves forward," the FBI said in a statement.

The Secret Service also requested the assistance of the U.S. Attorney's Office ,two senior U.S. law enforcement officials told NBC.

– Josephine Rozzelle

The Trump campaign went into "a complete communications lockdown," according to a message to staff obtained by NBC News.

"Everything is OK," wrote James Blair, Trump campaign and Republican National Committee political director. "Anyone who speaks with the press, even on background or off the record, will be found and terminated immediately."

"Refrain from commenting, speculating, posting on social media, etc. Complete and total lockdown," Blair added. "Your personal safety is of the utmost importance. Please exercise extreme caution during this time."

— Rebecca Picciotto