Charlie Kirk shooting witness says lack of security at the event troubled him

The shooter, who assassinated conservative activist Charlie Kirk and then vanished off a roof and into the woods, remained at large more than 24 hours later on Thursday, as federal investigators appealed for the public's help by releasing photos of the person they believe is responsible.

Investigators obtained clues, including a palm print, a shoe impression and a high-powered hunting rifle found in a wooded area along the path the shooter fled. But they had yet to name a suspect or cite a motive in the killing they were treating as the latest act of political violence to convulse the United States across the ideological spectrum.

The photos of a person in a hat, sunglasses and a long-sleeve black shirt, with a backpack, as well as a $100,000 reward for information leading to an arrest suggested that law enforcement thought tips from the public might be needed to crack the case.

Two people who were taken into custody shortly after Wednesday's shooting at Utah Valley University were later released, forcing officials to chase new leads on a separate person of interest they pursued Thursday.

A resident of Vineyard, in Utah, Henry Dells told the Associated Press that he got to ask Kirk a question and speak with him at the event on Wednesday. He said he was disturbed by the lack of security.

"I was looking around. I was like, I love Charlie, but I have a weird feeling that if something did happen, he would be in a very vulnerable position," he said.

Mourners left notes and flowers for Kirk at a makeshift memorial in Orem, Utah.