Orem: Charlie Kirk, a conservative activist and close ally of President Donald Trump who played an influential role in rallying young Republican voters, was shot and killed at a Utah college event in what the governor called a political assassination.

Authorities say Kirk was killed with a single shot from a rooftop on Wednesday. Whoever fired the gun then slipped away amid the chaos of screams and students fleeing the Utah Valley University campus. Federal, state and local authorities were still searching for an unidentified shooter early Thursday and working what they called “multiple active crime scenes."

“This is a dark day for our state. It's a tragic day for our nation," said Utah Gov. Spencer Cox. "I want to be very clear, this is a political assassination.”

Two people were detained on Wednesday, but neither was determined to be connected to the shooting, and both were released, Utah public safety officials said.

Authorities did not immediately identify a motive, but the circumstances of the shooting drew renewed attention to an escalating threat of political violence in the United States that in the last several years has cut across the ideological spectrum. The assassination drew bipartisan condemnation, but a national reckoning over ways to prevent political grievances from manifesting as deadly violence seemed elusive.