The person accused of fatally shooting conservative activist Charlie Kirk is 22-year-old Utah resident Tyler Robinson, according to five law enforcement officials briefed on the matter.

By Tom Winter, Michael Kosnar, Marc Santia, Jonathan Dienst, Ken Dilanian, Tim Stelloh and Matt Lavietes | NBC News

Kirk, co-founder of Turning Point USA and an influential voice in the Trump administration, was shot and killed Wednesday during an event at Utah Valley University, a public school south of Salt Lake City, according to Utah Department of Public Safety Commissioner Beau Mason. The event was organized by the school's chapter of Turning Point USA, a group founded by Kirk that organizes and mobilizes young conservatives.

He was later pronounced dead at a local hospital, Mason said.

A witness told NBC News he heard a gunshot and saw Kirk fall from his chair. Blood appeared to be coming from his neck, said Taylor Dufur, who said he was about 30 feet away from Kirk at the time.

Law enforcement officials said the shot was believed to have been fired by a person on the roof of a building. In an interview with NBC News, Mason said the single shot fired at Kirk traveled a distance of about 175 yards (160 meters).

Investigators tracked the person's movements on campus, through stairwells, and across a roof, Mason said at a news conference Thursday. After opening fire, Mason said, the person was seen jumping off a building and fleeing into a neighborhood.

The video released by authorities on Thursday captured the person they described as the shooter running across the roof of a building and descending to a grassy area below. The person can then be seen walking across a parking lot toward a busy road.