Charlie Kirks family attends hearing for murder suspect Tyler Robinson

Kirk was addressing a crowd from under a tent on 10 September as part of his American Comeback tour of college campuses, during which he invited attendees to debate him.

A shot rang out as he was speaking about gun violence; Kirk slumped over to the side.

Chris Bagley, one of four law enforcement witnesses expected to take the stand during the week-long hearing, had been stationed on a building above and realised from the noise that it had come from a rifle, not a handgun.

In court on Monday, he described a chaotic scene of people shouting and running and told the court that he was informed by law enforcement that a shooter had been taken into custody.

But he said he discovered suspicious evidence leading him to believe it might not be the right suspect.

Bagley said he found a screwdriver and an impression in gravel on a roof indicative of a sniper and then viewed security footage showing an individual dropping down and escaping from the area.

He described a telling impression the suspect had left behind.

“I could see the disturbance of gravel; to me, it looks like a sniper pad, a person that has been laying in a prone position, and you’ve got markings of elbows, knees and feet – where somebody was in the line of sight of where Charlie’s tent was.”

Robinson’s defense attorney Kathryn Nestor voiced several objections throughout the testimony, asking him about staffing, planning and surveillance on the day of Kirk’s event.

Another witness, David Hull, told the court he’d been working as an agent with Utah’s State Bureau of Investigation at the time of Kirk’s shooting. He testified that he reviewed surveillance video from the day of the shooting and saw Robinson “on campus … approximately four times throughout the day”.

Hull testified that Robinson appeared at the school twice before the attack, then again at the time of the shooting – then returned that evening, hours after Kirk’s death.

Prosecutors also played home surveillance footage from a neighbourhood near campus which they say shows Robinson parking his gray Dodge, then returning later and driving away.

The hearing is set to continue all week and will examine evidence and witnesses in the case to determine whether prosecutors have enough to present it before a jury at trial.