Charlie Kirk, a Trump ally and rightwing activist, was shot and killed during an event at Utah Valley University in Orem, Utah.
Utah Department of Public Safety Commissioner Beau Mason said the shooter is believed to have fired from a rooftop on campus.
Moments before the shooting, Kirk was answering questions about mass shootings and gun violence.
“Do you know how many transgender Americans have been mass shooters over the last 10 years?” an audience member asked. Kirk replied: “Too many.”
The questioner continued: “Do you know how many mass shooters there have been in America over the last 10 years?”
“Counting or not counting gang violence?” Kirk asked.
A single shot was then fired at around 12.20pm local time. Kirk was taken to hospital, where he later died.
US President Donald Trump confirmed the death on Truth Social, writing: “The Great, and even Legendary, Charlie Kirk, is dead. No one understood or had the Heart of the Youth in the United States of America better than Charlie. He was loved and admired by ALL, especially me, and now, he is no longer with us. Melania and my Sympathies go out to his beautiful wife Erika, and family. Charlie, we love you!”
Utah Governor Spencer Cox described the killing as a “political assassination”. “This is a dark day for our state. It’s a tragic day for our nation. I want to be clear that this is a political assassination,” he said.
Kirk is survived by his wife, Erika, and two children.