US President Donald Trump said on Friday that the suspect in the Charlie Kirk killing has been captured.

"With a high degree of certainty, we have him," Trump announced in a live interview on Fox News on Friday morning.

Trump said a minister who is also involved with law enforcement turned in the suspect to authorities.

"Somebody that was very close to him said, 'Hmm, that's him,'" Trump said.

Trump did not share the suspect's identity, but two people familiar with the investigation identified him to Reuters as Tyler Robinson, 22.

More than 7,000 leads and tips had poured in, officials said. Authorities have yet to publicly name the suspect or cite a motive in the killing, the latest act of political violence to convulse the US.

The FBI has released images of a "person of interest" in the murder of Kirk as Trump urged a peaceful response to the 31-year-old's killing.

The images show a young man, believed to be of college age, wearing a baseball cap, sunglasses and a black T-shirt, going up a flight of stairs. The FBI is offering a reward of up to $100,000 for information leading to the identification of the individual.

Utah Department of Public Safety Commissioner Beau Mason said on Thursday that, according to video footage, the suspect arrived at Utah Valley University at 11:52 am and climbed the stairwells to the roof of a building overlooking the event.

As Kirk was speaking to a crowd of about 3,000 at the campus around 12:20 pm as part of his "American Comeback" tour, a shot rang out. Video shows Kirk clutching his neck and collapsing, bleeding profusely from the neck.

He was taken to a hospital where he was pronounced dead.

Salt Lake City FBI Special Agent Robert Bohls said that a "high-powered bolt-action rifle", believed to be the gun used to kill Kirk, was recovered in a nearby wooded area through which investigators suspect the gunman fled.

Kirk, a conservative activist and close ally of Trump, played an influential role in rallying young Republican voters. He launched the conservative organization Turning Point USA in 2012 at the age of 18 and often made appearances at liberal-leaning campuses. He had a popular podcast and millions of followers on X.

Invoking reflections

Utah Governor Spencer Cox told reporters that Kirk's killing was "a political assassination".

"We just need every single person in this country to think about where we are and where we want to be, to ask ourselves: Is this what 250 years has wrought on us?"

Kirk's assassination leaves the nation to reckon with violence that has become increasingly political and public. At the same time, it's forcing universities to question whether more security is needed to protect people speaking their minds to campus audiences.

"It's going to rattle college campuses," said Nico Perrino, executive vice-president for the Foundation for Individual Rights and Expression. "Colleges are going to be concerned about these sorts of events moving forward, particularly if they are outside."

Most likely it will spur colleges to move large outdoor events into campus buildings, said Perrino, who is a frequent campus speaker himself. That's already the norm for most controversial visitors, who are typically hosted in auditoriums or classrooms that are easier to protect, he said.

Students at Utah Valley University on Thursday expressed shock and their broader fears as political divisions deepen across the country.

Dave Sanchez told AFP that witnessing the killing made him "sick to my stomach". "We watch him all the time and so it really does feel like one of your own family members, your own brother's been killed," said Sanchez, 26.

On Thursday, the US marked the 24th anniversary of the 9/11 attack with ceremonies in New York, at the Pentagon and in Shanksville, Pennsylvania. The commemorations were punctuated by moments of silence, the tolling of bells and the reading of the names of the nearly 3,000 killed.

The assassination of Kirk a day earlier prompted additional security measures at ground zero.

Agencies contributed to this story.

shiguang@chinadailyusa.com