Attendees at the campus event where US conservative activist Charlie Kirk was fatally shot on Wednesday have described mass panic after a shot was heard.

Kirk, 31, was killed after he was hit in the neck by a single bullet, which law enforcement believes came from a shooter on the roof of a nearby building.

The influencer and close Donald Trump ally had been speaking to about 3,000 people on his American Comeback Tour at Utah Valley University.

Videos on social media show Kirk talked about gun violence moments before he was shot.

One eyewitness told the BBC's US partner CBS: "Me and my buddies were having a good time just listening to what was going on and we just saw it, heard a loud shout, loud bang and then I saw his body actually in slow motion kind of fall over".

Porter LaFerber, a student at Utah Valley University who described himself as a "big fan" of Kirk's and was at the rally, told BBC Radio 4's Today programme that he was about 50ft (15m) away from Kirk.

"I was sitting there filming him, I cut my video and just then I heard this shot," he said.

"You don't really realise what's happened until it's happened. Charlie falls off his stool, everyone starts panicking."

LaFerber said he hid behind a "cement terrace" and then after about a minute of "not hearing another gunshot, I got up and just booked it to the closest building I could see".

In a video shared by news agency Reuters, an eyewitness called Danielle said she was closer to Kirk - about 15ft (5m) away.

"It was horrible," she said. "All I hear is screaming and I see people running and I'm like, 'it's not safe to run. It's not safe to get up'...And all I'm saying is, 'please, God, please, God, please, God,' because I don't want to die."

Jason Chaffetz, a former US congressman told Fox News he was at the event with his daughter when it happened.

"The shot came straight at him," he said, adding that "everyone hit the deck" and "scattered".

Adam Bartholomew, who was at the event interviewing counter-protesters who were speaking against Kirk's presence on campus, also said people initially dropped to the floor.

"There was confusion and people started scrambling for the exits," he told the BBC.

"Several people are in tears," he said of the atmosphere after the shooting.

Videos taken by witnesses show the rush to flee the scene after the shooting occurred.

A figure on the roof in separate video coverage appears to have been approximately 130m (142 yards) away from where Kirk was sitting.

Phil Lyman, a former Utah state representative, said he had been "involved politically" with Kirk and handed out baseball caps on stage with him before the event started.

"I went up to find some other people so I wasn't next to him when he was shot, and I don't know if I'm happy about that or that I wish I could've been there," he told the Today programme.

He added that: "3,000 kids basically watched somebody shot right in front of them, it's really traumatic. Really, really rough."

Two 17-year-olds, Grace Dishman and Grace Baird, spoke to the BBC from outside the police barricade where they had seen Kirk shot.

The girls, who are members of Turning Point groups at their high school, skipped school to attend the event with the approval of their parents.

Dishman said she never thought she would be anywhere near a shooting. Baird only wanted to get home. "I just want to hug my mom," she said.

Emma Pitts, a reporter at Utah-based Deseret News who attended the event, also described seeing the moment Kirk was shot.

"I'll never get the image out of my head," Pitts said.

Pitts added she was surprised that "nobody scanned our equipment, nobody scanned our bags, there was no security like that."

Bartholomew also said he was "surprised" that there was no security at the event. "Nobody stopped me or searched my bag."

The BBC has asked Utah Valley University for comment in response to security measures at the event.

The university had provided six security officers for the talk, in addition to Kirk's private security detail.

In the aftermath of the attack, students were on lockdown and unable to get back to their apartments until the early hours of the morning, as the shooter remained at large.

"It's unsettling around the campus right now, like I'm just trying to walk home, and it's just unsettling," said student Brock Anderson.