Justin Hickens says he was standing about 20 yards from Charlie Kirk as the influential conservative activist addressed a large crowd at Utah Valley University on Wednesday. Then, in the middle of Kirk’s remarks, Hickens heard “a big loud shot.”

“I saw a bunch of blood come out of Charlie,” Hickens told NBC News’ Tom Llamas. “I saw his body kind of kick back and go limp, and everybody dropped to the ground.”

When people realized Kirk had been shot, they started running from the outdoor pavilion area, some knocking over barricades as they fled, Hickens said.

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Hickens is one of scores of people who had gathered to see Kirk, a leading conservative voice and prominent ally of President Donald Trump and who regularly holds events on high school and college campuses.

In videos and images posted on social media, attendees can be heard yelling and scrambling for safety. In interviews, students described hearing a booming “pop” noise and seeing a bloodied Kirk fall back in his chair.

Kirk later died at a hospital. He was 31.

Tyler McGettigan, another attendee, told NBC News he was surprised that he wasn’t asked to go through security to get in.

The event required a ticket with a scannable code, which McGettigan printed out and brought with him, he said in an interview. But he did not need the ticket to get into the amphitheater where Kirk spoke, McGettigan said.

“No one checked the barcode or the QR code. There was no checkpoint to get in. It was literally, anyone could walk in if they wanted,” McGettigan said.

Hickens and a third attendee also said there were no metal detectors posted outside.

Isaac, who did not provide his last name, told NBC News affiliate KSL that there were “no checkpoints, nothing, to get in here.”

Isaac said the scene inside the amphitheater was “surreal.” He said he saw blood “shooting out” of Kirk’s neck as attendees “hit the floor.” He said he and his friends “bolted out of there,” believing a mass shooting may have been underway.

Authorities do not have a suspect in custody.

This is a developing news story. Please refresh for updates.