US authorities have released footage of the suspected shooter fleeing the scene after gunning down pro-Trump activist and political figure Charlie Kirk during his event at Utah Valley University.

More than 24 hours after Kirk was shot dead, FBI Director Kash Patel, Utah Governor Spencer Cox, and Commissioner of Public Safety Beau Mason held a press conference today pleading for the public's help.

"We need as much help as we can possibly get", Cox said, adding that the FBI has already received more than 7000 calls in the largest number of tips since the Boston Marathon bombing in 2013.

"We cannot do our job without the public's help."

Officials shared a video of the person of interest fleeing the rooftop, jumping to the ground and then running across the parking lot.

The suspected shooter then crosses the road and disappears into a wooded area, where officers later found a rifle.

Authorities also circulated new images of the person of interest, dressed in a black shirt with an American flag and eagle on it, Converse shoes, a cap with a triangle on it, sunglasses and a backpack. 

The FBI has announced a US$100,000 ($150,000) reward for the killer's apprehension as the manhunt continues into a new day.

Here's everything we have learnt about the suspected shooter so far.

Who shot Charlie Kirk?

Authorities are still working to track down the person who shot Kirk at his event at Utah Valley University on Thursday (Wednesday US time).

The suspect has not yet been identified, but is believed to be the person pictured.

The FBIreleased the images and announced a US$100,000 ($150,000) reward for the killer's apprehension.

The Utah Department of Public Safety released more images of the same suspect.

Photos show the suspect wearing a black shirt with an American flag and eagle on it, Converse shoes, a cap with a triangle on it, sunglasses and a backpack. 

Officials said that the suspect appeared to be of college age and blended in well on campus.

Multiple videos of the suspect have also been released to the public, including one clip that shows the suspect fleeing the scene of the shooting.

In it, the suspect can be seen running across the Utah Valley University Losee Centre roof after fatally shooting Kirk.

The shooter jumps to the ground, runs across the parking lot and crosses the road into a wooded area.

Other footage of the incident shows a dark shape, which may show a person lying down on the roof.

Footage obtained and broadcast by TMZ also appeared to show the suspect walking towards the university campus where Kirk was shot.

They appear to be limping in the clip.

The Utah Department of Public Safety said investigators had collected a number of additional details for forensic analysis, including"a footwear impression, a palm print, and forearm imprints".

Mason said they still have"no idea" where the shooter is.

"We're exploring leads for individuals that live close by," he said.

"We literally have persons of interest, tips coming in on the tip line, that are spanning far and wide."

Cox warned there was false information about the shooter circulating on social media.

"There is a tremendous amount of disinformation," he said.

"Our adversaries want violence. We have bots from Russia, China, all over the world that are trying to instil disinformation and encourage violence. I would encourage you to ignore those, to turn off those streams."

Was the shooter on a roof?

It is believed Kirk was shot from a rooftop on the Utah Valley University campus where he was hosting an event.

Footage from the incident showed what might have been a person on the Utah Valley University Losee Centre roof near the site of Kirk's shooting.

Kirk's former head of security, Gregory Schaffer, told the Associated Press that Kirk's security was usually focused on preventing threats like stage-crashers.

"You don't expect a threat to come from 200 yards away on a college campus," he said.

"We didn't have enough manpower to put people on the rooftops, we didn't have the funding to pay for a pair of binoculars that cost $3000."

How far away was the shooter?

CNN claimed the shot was taken from about 137 metres away, based on the work of cartographers and open-source intelligence experts.

Audio forensics expert Rob Maher told CNN he believed the bullet that struck Kirk was fired from a distance of 153 metres away.

He also inferred the bullet had been travelling at about 800m/s.

A former law enforcement ballistic expert told the UKIndependent the shooter did not have to be highly experienced to make such a shot.

"He didn't have to be highly trained as a sniper to make that shot from 200 yards (180 metres), because 200 yards with the right rifle and the right optics is not that far," said former FBI supervisory special agent Dennis Franks.

But he also said hitting a target of that distance outside a shooting range was vastly different to a crowded public setting, like at Kirk's event.

"To do it under the stress of a live situation, he was either skilful or lucky."

Suspected murder weapon revealed

In the 24 hours after Kirk's death, law enforcement confirmed they had found a"high-powered" rifle believed to be the murder weapon.

Today, CNN quoted a law enforcement official as saying it is a Mauser bolt action.30-06 calibre rifle with a long-distance scope.

The official said a single shell casing remained inside the bolt mechanism.

Maher told CNN it appeared Kirk was struck by a single bullet fired by a high-powered weapon and travelling faster than the speed of sound.

According to the Utah Department of Public Safety, members of the public have also sent in tips about the alleged murder weapon.

"There are reportedly photos of a weapon and various details about that firearm and ammunition, including inscriptions and symbols," the department said in a release.

"At this time, we are not able to provide further details on the content of those inscriptions."

Why did the shooter target Charlie Kirk?

No information has been released as to the shooter's motive.

Kirk was an outspoken right-wing and pro-Trump activist and received"thousands" of threats, according to a post on his X profile from his organisation Turning Point USA.

"Charlie was no stranger to threats. He received thousands throughout his life," the post read.

"But he always prioritised reaching as many young Americans as possible over his own personal safety."

President Donald Trump has repeatedly blamed the"radical left" for the shooting, without providing evidence.

"We have a radical left group of lunatics out there, just absolute lunatics, and we're going to get that problem solved. I'm only concerned for the country," he said today.

He ordered all American flags, including the one on top of the White House, to be flown at half mast and announced that Kirk will receive a posthumous Presidential Medal of Freedom.

Tributes have poured in for Kirk today as Vice President JD Vance escorted his coffin on Air Force Two to return him to his hometown of Phoenix.

Kirk's wife, Erika, was on board.

Trump said he had a"long talk" with her.

"I spoke to Erika, his wife, and we had a long talk, and she's devastated," he told reporters as he departed the White House for New York City earlier today.

"She is absolutely devastated, as you can imagine."

Does Utah have the death penalty?

Yes, Utah is among the 27 US states with the death penalty.

Cox reminded the world of that on national television today, warning"we still have the death penalty here in the state of Utah".

At the press conference later on, he confirmed that authorities will be pursuing the death penalty in this case.

"We've been working with our attorneys, getting everything that we need, affidavits ready so that we can pursue the death penalty in this case," he said.