Charlie Kirk, a 31-year-old conservative activist and media personality, was killed on Wednesday by a single gunshot to the neck while speaking at an event at Utah Valley University.

The event, in Orem, Utah, was held at an outdoor stage, where around 3,000 people had gathered to hear Mr. Kirk speak. Gov. Spencer Cox, Republican of Utah, described the shooting as a “political assassination.”

Here is a visual timeline of how the shooting unfolded.

Noon on Wednesday

Mr. Kirk was at Utah Valley University for the event, which was free to attend and scheduled to start at noon local time. The event was the first of a 15-stop itinerary on what was called the American Comeback Tour, which had planned appearances at college campuses across the United States.

As the event began, Mr. Kirk was addressing the crowd and answering questions while sitting under a tent, emblazoned with the tour’s name, in the outdoor courtyard of the school’s main campus.

Around 12:20 p.m.

About 20 minutes after he began speaking, Mr. Kirk was shot. Videos recorded before and after the shooting show a person on the roof of the Losee Center, about 150 yards away.

Seconds before the shooting, Mr. Kirk was asked a question about mass shootings in America.

A video taken just after the shooting captured someone running on the roof of the Losee Center.

Videos also showed people fleeing from the event in the immediate aftermath of the shooting.

As news of the shooting spread, statements of shock and horror poured in on social media from prominent figures on both the right and the left.

The university announced that the campus was closed and classes were canceled until further notice. It also said that police were going to building to building to escort people off campus, and that roads were closed.

2:40 p.m.

About two hours after Mr. Kirk was shot, his spokesman announced that he had died. President Trump posted a tribute to him on Truth Social and ordered American flags at public buildings to be lowered to half-staff until Sunday evening.

Mr. Kirk had been taken in a private vehicle to a hospital, where he was pronounced dead, said Beau Mason, the commissioner of the Utah Department of Public Safety.

4 p.m.

At a news conference, officials said they believed this was a targeted attack against Mr. Kirk. “There was one shot fired and one victim,” Mr. Mason said.

Officials said that two people had been taken into custody by late Wednesday as part of their investigation, but both were released without being charged in relation to the shooting.

The F.B.I. director, Kash Patel, posted on social media late Wednesday that a subject had been apprehended for Mr. Kirk’s murder, but not long after, posted again that the person had been released and that the investigation continued.

Riley Mellen contributed reporting.