“With a high degree of certainty, we have him,” Trump announced in a live interview on Fox News Chanel on Friday morning local time (Friday night AEST).

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.

According to four sources familiar with the matter, a person is indeed in custody and being questioned in connection to the fatal shooting.

The person is still being questioned as of Friday morning, the sources told CNN.

Federal investigators and state officials on Thursday had released photos and a video of the person they believe is responsible.

Kirk was shot as he spoke to a crowd gathered in a courtyard at Utah Valley University in Orem.

More than 7000 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 United States.

The attack, carried out in broad daylight as Kirk spoke about social issues, was captured on grisly videos that spread on social media.

The videos show Kirk, a close ally of Trump who played an influential role in rallying young Republican voters, speaking into a handheld microphone when suddenly a shot rings out.

Kirk reaches up with his right hand as blood gushes from the left side of his neck.

Stunned spectators gasp and scream before people start running away.

The shooter, who investigators believe blended into the campus crowd because of a college-age appearance, fired one shot from the rooftop, according to authorities.

Video released showed the person then walking through the grass and across the street before disappearing.

“I can tell you this was a targeted event,” said Robert Bohls, the top FBI agent in Salt Lake City.

Trump, who was joined by Democrats in condemning the violence, said he would award Kirk the Presidential Medal of Freedom, the highest civilian honour in the US Vice President JD Vance and his wife, Usha, visited with Kirk’s family on Thursday in Salt Lake City.

Vance posted a remembrance on X chronicling their friendship, dating back to initial messages in 2017, through Vance’s Senate run and the 2024 election.

“So much of the success we’ve had in this administration traces directly to Charlie’s ability to organise and convene,” Vance wrote.

“He didn’t just help us win in 2024, he helped us staff the entire government.”

Kirk’s casket was flown aboard Air Force Two from Utah to Phoenix, where his nonprofit political youth organization, Turning Point USA, is based.

Trump told reporters he plans to attend Kirk’s funeral. Details have not yet been announced.

Kirk was taking questions about gun violence

Kirk was a conservative provocateur who became a powerful political force among young Republicans and was a fixture on college campuses, where he invited sometimes-vehement debate on social issues.

One such provocative exchange played out immediately before the shooting as Kirk was taking questions from an audience member about gun violence.

The debate hosted by Turning Point at the Sorensen Centre on campus was billed as the first stop on Kirk’s “American Comeback Tour”.

The event generated a polarising campus reaction.

An online petition calling for university administrators to bar Kirk from appearing received nearly 1000 signatures.

The university issued a statement last week citing First Amendment rights and affirming its “commitment to free speech, intellectual inquiry and constructive dialogue”.

Last week, Kirk posted on X images of news clips showing his visit was sparking controversy. He wrote, “What’s going on in Utah?”

Attendees barricaded themselves in classrooms

Some attendees who bolted after the gunshot rushed into two classrooms full of students.

They used tables to barricade the door and to shield themselves in the corners.

Someone grabbed an electric pencil sharpener and wrapped the cord tightly around the door handle, then tied the sharpener to a chair leg.

On campus Thursday, the canopy stamped with the slogan Kirk commonly used at his events — “PROVE ME WRONG” — stood, dishevelled.

Kathleen Murphy, a longtime resident who lives near the campus, said she has been staying inside with her door locked.

“With the shooter not being caught yet, it was a worry,” Murphy said.

Meanwhile, the shooting continued to draw swift bipartisan condemnation as Democratic officials joined Trump and other Republican allies of Kirk in decrying the attack, which unfolded during a spike of political violence that has touched a range of ideologies and representatives of both major political parties.