Tyler Robinson, the suspect in the killing of the right-wing activist Charlie Kirk, evaded detection for hours before climbing on a roof, where the police say he shot and killed Mr. Kirk during an outdoor event at Utah Valley University on Wednesday. The authorities arrested Mr. Robinson on Thursday night after a 33-hour manhunt.

A New York Times review of videos, a 3-D analysis of the scene and an affidavit released on Friday shed new light on the gunman’s movements in the moments leading up to the shooting and immediately after.

Arrival on campus

Charlie Kirk’s event, which had been scheduled for noon on Wednesday, was free to attend, and there were no visible barriers to access of the Utah Valley University campus that day, according to a Times review of images.

Mr. Robinson arrived on campus in a gray Dodge Challenger at 8:29 a.m. local time, nearly four hours before the shooting, officials said. Security camera footage reviewed by investigators showed the gunman wearing a different set of clothing than what he was seen wearing at the time of the shooting.

It’s unclear what Mr. Robinson did for several hours after arriving on campus. Investigators said they were able to track his movements starting at around 11:50 a.m., when he was captured on video crossing a grassy area into a parking lot next to campus. A video published on Thursday by TMZ showed a person wearing similar clothing to Mr. Robinson’s near where authorities said he was spotted.

Mr. Robinson then walked across the parking lot toward a pedestrian tunnel. Investigators said he paused at the top of the stairs at 11:53 a.m. to pull out his phone, before continuing into the tunnel.

Images released by the F.B.I. show him ascending the stairs of a parking garage adjoining the tunnel.

Investigators noted that Mr. Robinson was walking with a distinctive gait, with the mobility of his right leg appearing to be restricted. They did not provide information on where Mr. Robinson went immediately after exiting the garage.

Nearing the site of shooting

At 12:02 p.m., according to the authorities, Mr. Robinson was seen walking on the north side of the Losee Center — the building where they say he would later climb to shoot Mr. Kirk. According to the affidavit, he entered the building from the southeast side, then, 13 minutes later, walked up a set of stairs to a walkway abutting the Losee Center.

He climbed over a short wall and crouched behind it, investigators said. He was then seen on video running across the roof — his limp now gone.

The rooftop shooting of Charlie Kirk

By 12:22 p.m., the gunman was in a prone position on the roof of the Losee Center facing the courtyard, where Mr. Kirk was speaking in front of about 3,000 people.

A 3-D analysis of the shooting site showed no apparent barriers that would have blocked the gunman’s line of sight to Mr. Kirk, who was seated under a tent about 430 feet away.

Those who attended the event said that security seemed light for an open amphitheater event with a polarizing figure like Mr. Kirk. Only six campus police officers were present, according to Utah Valley University’s chief of police, who added that Mr. Kirk also had a private security team that traveled with him.

For events of this size and scope, security experts recommend a comprehensive plan, working with local and federal law enforcement agencies to put in place security protocols, which could include establishing a perimeter with safety checkpoints and securing problem areas like rooftops.

Mr. Kirk often traveled with a five-person detail, with one guard stationed onstage and others arrayed in front and back, said Greg Shaffer, who had protected Mr. Kirk for seven years. The team worked with the campus police on evacuation and security plans.

A Times analysis of footage from the event showed several people with what appeared to be earpieces facing the crowd minutes before the shooting. These individuals were also seen rushing to Mr. Kirk as soon as he was shot and transporting him to a car.

It’s unclear how visible the shooter would have been to the security detail on the ground near the tent, according to Times 3-D analysis. The shooter may have been hidden behind a parapet while lying in a prone position on the roof and dressed in dark clothing.

At 12:23 p.m., the gunman fired a single shot at Mr. Kirk, killing him. As the crowd dispersed, those who appeared to be security personnel quickly surrounded him.

Video also showed two campus police officers rushing in from behind the tent.

A fast escape

Immediately after the shooting, the gunman made a quick escape.

Video released by officials on Thursday showed him running toward the opposite end of the Losee Center, where he jumped at least 15 feet onto the ground.

He then headed back toward Campus Drive, and according to the authorities, crossed the road into a nearby wooded area. The gun used in the shooting was later recovered here, along with bullet casings engraved with various messages.

The manhunt ended more than 200 miles away, officials said, after a phone call from a family friend of Mr. Robinson, who is being held in the Utah County Jail.