A week after the Capitol Police officer who fatally shot Ashli Babbitt as she attempted to climb through the broken part of a door to the Speaker’s Lobby in the U.S. Capitol during the Jan. 6 riot was exonerated, he spoke publicly for the first time and provided harrowing details about what happened inside the building during the insurrection, and about the threats to his life since the attack.

Lt. Michael Byrd told Lester Holt during an exclusive NBC interview broadcast on Thursday that he saved “countless lives” when he used deadly force to prevent Babbitt and other rioters from breaching the House chambers as lawmakers were in the process of certifying the results of the presidential election. Byrd had never been officially publicly identified, but he said he has still been the target of death threats since the incident.

“They talked about killing me, cutting of my head, very vicious and cruel things,” Byrd said. “There were some racist attacks as well. It’s all disheartening because I know I was doing my job.”

Some supporters of Former President Donald Trump have painted Babbitt, a 35-year-old Air Force veteran, as a martyr since her death and expressed dissatisfaction after the U.S. Capitol Police exonerated Byrd earlier this month.

“USCP’s Office of Professional Responsibility (OPR) determined the officer’s conduct was lawful and within Department policy, which says an officer may use deadly force only when the officer reasonably believes that action is in the defense of human life, including the officer’s own life, or in the defense of any person in immediate danger of serious physical injury,” Capitol Police said in a statement.

The declaration came after the Justice Department announced in April that no charges would be brought against the officer.

Byrd said he had concerns about his safety as he made the decision to reveal his identity. “That’s something that is frightening. I believe I showed the utmost courage on Jan. 6 and it’s time for me to do that now.”

Five people died as a result of the riot, including Capitol Police Officer Brian Sicknick. Hundreds of Capitol and D.C. officers were injured and more than 600 people have been charged for roles in the riot.

Byrd said he could hear radio calls about breaches of areas of the building and about officers being overrun and injured as he defended the Speaker’s Lobby, where some 80 lawmakers in that section of the building were trapped, with the invading horde on the other side of the door.

“Once we barricaded the doors, we were essentially trapped where we were,” Byrd told Holt. “There was no way to retreat. No other way to get out. If they get through that door, they’re into the House chamber and upon the members of Congress,” Byrd said.

Byrd also appeared before lawmakers and instructed them to put on gas masks in the midst of the chaos. He said he warned Babbitt and other rioters — who had broken the glass section of the door after other officers stepped aside from their positions in front of it — to move back before firing a single, fatal shot as Babbitt ignored him and tried to climb through the door to the Speaker’s Lobby.

Byrd said that at the moment he fired the weapon, Byrd was “posing a threat to the United States House of Representatives.”

On social media, some users strongly criticized Byrd. “Make this a white cop shooting a BLM rioter and the whole country would be on fire right now,” wrote conservative commentator Matt Walsh.

Fox News host Tucker Carlson responded to Byrd’s interview saying, “She was an unarmed protester. I don’t think we execute unarmed protesters, do we? Well we did. No one’s apologized for it. He’s a hero.”

In contrast, some lawmakers thanked Byrd for his bravery. “Officer Michael Byrd saved my life,” wrote Michigan Rep. Dan Kildee.

“Lt. Michael Byrd did his job,” wrote journalist Wajahat Ali.

Attorney and activist Chris Hahn shared his thoughts in a straightforward fashion. “LT Michael Byrd is a hero. Ashli Babbitt was a terrorist. End of discussion,” he wrote.

Trump said in a statement on Aug. 11 that Babbitt was “murdered”, “The Radical Left haters cannot be allowed to get away with this. There must be justice!”

Babbitt’s family is seeking “well above $10 million” from the U.S. Capitol Police in a upcoming lawsuit.