A Michigan sheriff has revealed that the 15-year-old gunman who he said carried out a deadly rampage at Oxford High School never knocked on the door of a barricaded classroom while pretending to be a sheriff's deputy, as a widely-circulated cellphone video would suggest. Ethan Crumbley was arrested within minutes of deputies' arrival at the school on Tuesday. Prosecutors announced on Wednesday that they have charged the 15-year-old as an adult with 24 criminal counts, including four charges of murder and terrorism. The school shooting in suburban Detroit - the deadliest in the US since 2018 - claimed the lives of four students and left seven others wounded, one of them critically. Three of the students who were killed were identified as 16-year-old Tate Myre, 14-year-old Hana St. Juliana, and 17-year-old Madisyn Baldwin. A fourth student, 17-year-old Justin Shilling, succumbed to his jaw and head wounds on Wednesday. During a press conference on Wednesday, Oakland County Sheriff Michael Bouchard sought to clear up some 'false information,' which he said social media have been 'ginning up', including allegations that the his office had been warned about the coming shooting. Oakland County Sheriff Michael Bouchard said on Wednesday that Oxford High School shooting suspect Ethan Crumbley, 15, never knocked on a classroom door during Tuesday's deadly rampage Video shot inside a classroom showed someone knocking at the door, claiming to be a sheriff's official. Sheriff Bouchard said it was most likely a plainclothes detective. Freshman Mark Kluska recorded the incident inside his sign language class Kluska and his classmates escaped through a first-story window and ran across the yard to safety (pictured) Ethan Crumbley, 15, is being charged as an adult with two dozen counts, including murder and terror Bouchard paid special attention to a recording that was taken by Oxford freshman Mark Kluska, which showed students huddling inside a classroom when someone knocked on the door. 'A video was disseminated rather widely that showed the students in the classroom and depicted someone knocking on the door, and pretty much the allegation was that was the suspect,' Bouchard told reporters. Kluska told CNN he was in his sign language class when an active shooter lockdown was announced, prompting his teacher, Moises Cortez, to shut the classroom door and secure it with a metal doorstop so no one could kick it in from the outside. 'I started realizing it was real when I began to hear yelling,' Kluska told the network. The freshman said his teacher switched off the lights and told his students to huddle in a corner 'because this might not be a drill and he wants to be safe.' As seen in Kluska's video, someone who was previously thought to be the gunman raps on the door. 'Sheriff's office,' the person at the door is heard saying in the footage. 'You can come out.' Students look at one another as one whispers, 'He said it's safe to come out.' But the teacher refuses to open the door, saying: 'We're not willing to take that risk right now.' The person shouts something inaudible before calling his classmate 'bro,' prompting the teacher to signal his students to quickly escape through a first-story window. Kluska said they ran across the snow-covered courtyard to another part of the building, where a real law enforcement officer led them to safety. 'We've now been able to determine that was not the suspect,' the sheriff announced on Wednesday. 'More than likely it was one of our plainclothes detectives, and he may have been talking...in a conversational manner to try to bring them down from the crisis, to say, "Come on, bro, let's get out of the classroom, let's get you outside." 'The suspect, we have now confirmed by analyzing all of the video from the time [the shooting] began to the time we took him into custody, never knocked on a door.' Bouchard also sought to dispel other rumors, which he said have been making the rounds on social media, including that his office had received advance notice that a shooting was about to take place at the high school. He dismissed those claims as 'false.' The shooting took place at around lunchtime in Oxford Township, Michigan, leading to the teenage suspect's arrest within 5 minutes of the first 911 call coming in Parents walk away with their kids from the Meijer's parking lot where many students gathered following the shooting at Oxford High School Emerson Miller, right, leans on her friend Joselyn's shoulder as they listen to Jessi Holt, pastor at LakePoint Community Church, during a prayer vigil at the church after the Oxford High School shooting on Tuesday night An Oakland County Sheriff's deputy hugs family members of a student in the parking lot of Oxford High School on Wednesday 'The threat that we were notified in advance was one from November 11, that actually we did investigate and it was determined to be from Georgia, not Oakland County, and had no relationship to Oxford schools and was cleared as such,' Bouchard stated. 'It has nothing to do with this event,' the sheriff added, referring to Tuesday's shooting. 'We received no information of [Crumbley] prior to the shooting.' Bouchard confirmed that the school, however, did have prior contact with Crumbley and his parents, including on the morning of the incident, 'for behavior in the classroom that they felt was concerning.' The sheriff said his investigators did not learn of the meeting between Crumbley's parents and school officials until after his arrest. 'So please, I remind everyone, be weary of social media and what's spread because it's hurtful to the community, it's hurtful to the victims, and it spreads false, sad misinformation,' Bouchard pleaded. All rights reserved for this news site (dailymail) and under his responsibility