More photos of person of interest in Charlie Kirk assassination after high-powered rifle recovered

The shooter who assassinated conservative activist Charlie Kirk and then vanished off a roof and into the woods remains at large more than 24 hours later as federal investigators appeal for the public's help by releasing photos of the person they believe is responsible.

Investigators obtained clues, including a palm print, a shoe impression and a high-powered hunting rifle found in a wooded area along the path the shooter fled.

But they had yet to name a suspect or cite a motive in the killing they were treating as the latest act of political violence to convulse the United States across the ideological spectrum.

LIVE: Manhunt for assassin enters second day

The photos of a person in a hat, sunglasses and a long-sleeve black shirt, with a backpack, as well as a $US100,000 reward for information leading to an arrest suggested that law enforcement thought tips from the public might be needed to crack the case.

Two people who were taken into custody shortly after the shooting at Utah Valley University were later released, forcing officials to chase new leads on a separate person of interest they pursued.

READ MORE: What we know about the shot that killed Charlie Kirk

Authorities planned another news conference later today with FBI Director Kash Patel and Utah Governor Spencer Cox in the line-up of speakers.

One clue in the investigation was a Mauser .30-calibre, bolt-action rifle found in a towel in the woods.

A spent cartridge was recovered from the chamber, and three other rounds were loaded in the magazine, according to information circulated among law enforcement and described to The Associated Press.

The weapon and ammunition were being analysed by law enforcement at a federal lab.

READ MORE: Joe Rogan reacts to Charlie Kirk's death as he is told live on air

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

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

Kirk can be seen reaching 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 a single shot from the rooftop where they were perched before jumping off.

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

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, while Vice President JD Vance and his wife, Usha, arrived in Salt Lake City to visit with Kirk's family.

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 organisation, Turning Point USA, is based.

Trump told reporters he plans to attend Kirk's funeral.

Details have not 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.

He was shot while attending one such event yesterday, a debate hosted by Turning Point at the Sorensen Centre on campus in what 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?"

One such provocative exchange played out immediately before the shooting, as he was taking questions from an audience member about gun violence when the shot was heard.

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.

Madison Lattin was watching a few dozen feet from Kirk's left when she heard the bullet hit him.

"Blood is falling and dripping down, and you're just like so scared, not just for him but your own safety," she said.

On campus Thursday, the canopy stamped with the slogan Kirk commonly used at his events "PROVE ME WRONG" stood, disheveled.

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.

"The murder of Charlie Kirk breaks my heart. My deepest sympathies are with his wife, two young children, and friends," Gabrielle Giffords, the former Democratic congresswoman who was wounded in a 2011 shooting in her Arizona district, said.