Authorities said Tyler Robinson, 22, expressed opposition to conservative activist Charlie Kirk’s viewpoints before allegedly carrying out the targeted killing, highlighting growing concerns about political violence in the U.S.

Utah Governor Spencer Cox said Robinson had become “more political” in recent months and confessed to a family friend that he was responsible. Key evidence included bullet engravings found on a rifle believed to be used in the attack and messages shared by Robinson’s roommate.

Robinson, who is believed to have acted alone, was arrested early Friday, a development announced by President Donald Trump, who praised Kirk as someone dedicated to helping young people.

Kirk, co-founder of Turning Point USA, was shot while speaking at a debate at Utah Valley University and was pronounced dead hours later. Authorities recovered a high-powered, bolt-action rifle near the scene and released photos and video of the suspect prior to the arrest, the Associated Press has reported.

More than 7,000 tips were submitted to law enforcement, though officials have not yet determined a clear motive for the politically charged killing, which Utah’s governor called an “attack on the American experiment.”