"On April 10th, we went to Dover Air Force Base to welcome my husband back home with our whole family. But this time it was not a celebration," De Alencar told CNN on Thursday night.
Two days after her husband came home, Trump called as she sat with an Army casualty officer.
'Men like in the movies'
De Alencar 's world changed on April 8. Her daughter had gone to the car to retrieve her phone when she tearfully asked her to come downstairs.
"My daughter ... told me that men like in the movies were at our front door," De Alencar said.
She paced up and down the stairs before she finally went to the door of their home at Eglin Air Force Base in Florida.
Staff Sgt. Mark R. De Alencar was killed in Afghanistan in April.
When she got there, two Army men told her that her husband had been shot dead in Afghanistan. They said an Army casualty assistance officer would be sent to her house shortly.
"He celebrated his 37 birthday on April 1 and seven days after his birthday, he was dead," she said.
Call from President Trump
Four days later, on April 12, De Alencar was with the casualty officer when his phone rang. When the casualty officer handed it to her, the person on the other end told her Trump wanted to talk to her.
"Natasha," Trump said in the call filmed by her children and the video provided to CNN on Thursday night by De Alencar.
"I'm so sorry to hear about the whole situation. What a horrible thing ... he's an unbelievable hero and you know all the people that served with him are saying how incredible he was ... ," Trump said.
De Alencar said Trump had researched her husband and was familiar with the awards he had received.
She described herself as a Democrat who does not "do politics." As a father himself, she said, Trump appeared to understand the magnitude of her loss. In the call, Trump talked about her children, especially her oldest son, who plays college football.
"It became nothing about politics but a person who understood, and that is what he gave to us," De Alencar said.
'Their father was a great hero'
The conversation lasted about five minutes, she said. Before the end of the conversation, Trump gave her a message for her children.
"Tell them their father was a great hero that I respected," Trump said.
The President told De Alencar to take care of herself and extended an invitation to visit the White House. "If you're around Washington, you come over and see me in the Oval Office," he said.
De Alencar said it was important to record the call.
"All you got is memories and having the commander-in- chief call you for five minutes is an important memory," she said.
Mark and Natasha De Alencar got married in 2008 after 15 years together. He served in the military for 10 years, and was the son of an Army veteran.
"He is the most amazing, humblest and very soft spoken," she said. "He was a Ranger and a Green Beret. He made you want to do better. I am better mother and woman because of him."
The couple have five children between them: Deshaun Osbourne, 20, Octavia Osbourne, 18, Rodrigo De Alencar 16, Tatiyana De Alencar 13, and Marcos De Alencar, 5.
"I know they are hurting and they don't know what the future holds because I know what they are going through," she said. "That is the only thing I can comment on from my heart because that is what I know is true."