Tyler Robinson had become “more political� in the run-up to the shooting and mentioned during a dinner with family that Kirk would be visiting Utah, Gov. Spencer Cox said at a news conference. The Republican governor cited as evidence engravings on bullet casings found in the rifle that authorities believe was used in the attack, as well as chat app messages attributed to the suspect that a roommate shared with law enforcement.

The governor credited Robinson's family with helping turn him over to authorities.

“Ladies and gentlemen, we got him,� Cox said soon after the arrest was first heralded by President Donald Trump on the Fox News show “Fox & Friends.�

Robinson is believed to have acted alone, and the investigation is ongoing, Cox said. He was arrested on suspicion of capital murder, weapons and obstruction offenses. He was expected to be formally charged Tuesday ahead of an initial court appearance.

Robinson’s arrest late Thursday capped a frenetic day-and-a-half search that just hours earlier seemed stuck when authorities pleaded for tips and leads from the public. The assassination while Kirk was speaking at Utah Valley University reverberated across the country because of his outsize influence in conservative circles, his close connections with Trump and because of the questions it raised about the escalating toll of political violence that has spanned the ideological spectrum.

“This is our moment: Do we escalate or do we find an off-ramp?� Cox asked, making an impassioned plea for young people to bridge differences through common ground rather than violence. “It’s a choice.�

New details on evidence

Authorities, who have yet to reveal a motive, described evidence they said shed potential light on the slaying.

Ammunition found with the weapon was engraved with taunting, anti-fascist and meme culture messages, including one bullet casing that said, “Hey, fascist! Catch!� Cox said.

In addition, a roommate shared with authorities messages from the chatting app Discord that involved a contact named Tyler and discussed a rifle wrapped in a towel, engraved bullets and a scope, the governor said. A Mauser .30-caliber, bolt-action rifle was found in a towel in a wooded area along the path investigators believe Robinson took after firing a single shot from a distant roof and then fleeing.

The clothes the suspect wore when confronted by law enforcement late Thursday matched what he had on when he arrived on campus, and a family member confirmed he drove a gray Dodge Challenger like the one seen in surveillance video that recorded Robinson driving to the university the day of the shooting, Cox said.

Robinson’s father recognized him from the photos released by the FBI and told him to turn himself in. Robinson refused at first, but then changed his mind, according to a law enforcement official who spoke on the condition of anonymity to discuss an ongoing investigation. His father contacted their youth pastor, who also occasionally works with the U.S. Marshals and called the agency so Robinson could turn himself in.

Meanwhile, investigators continued to dig into the background of Robinson, who was admitted to Utah State University, about 80 miles north of Salt Lake City, on a prestigious academic scholarship, according to a video of him reading his acceptance letter posted to a family member’s social media account. However, he attended for only one semester in 2021, a university spokesperson said.

Robinson currently is enrolled in an electrical apprenticeship program at Dixie Technical College near his hometown, a suburb of St. George in southern Utah.

He is registered as an unaffiliated voter and does not appear to have a prior criminal record. His address was still listed as his parents' home, about a 3.5-hour drive south of the campus where Kirk was shot.

Family members of Robinson did not immediately return messages seeking comment. It was not clear if he had a lawyer.

At his family’s home, window coverings were drawn, and a pickup truck blocked access to the driveway. There was a heavy law enforcement presence, with several police vehicles parked along the street, which was closed at both ends.

‘He didn’t deserve this'

Kirk was a conservative provocateur who became a powerful political force by rallying young Republican voters and was a fixture on college campuses, where he invited sometimes-vehement debate on social issues.

Kirk co-founded the nonprofit political organization Turning Point USA, based in Arizona. He had been speaking at a campus debate on the first stop of his “American Comeback Tour,� at the time of Wednesday’s shooting.

He was taking questions from an audience member about gun violence when a shot rang out. Kirk reached up with his right hand as blood gushed from the left side of his neck.

Two days later, law enforcement officers continued to sweep the Utah Valley campus for evidence while the announcement of an arrest brought some relief.

“There’s been this like really heavy, dark weight pressed over my heart and soul for the last two days, and waking up to the news of the shooter being captured today, it is a great thing,� said Creighton Baird, who was close enough to the stage to see horrific images that continue replaying in his mind.

Classes at Utah Valley University were scheduled to start back up Wednesday and the school announced that there would be “increased security on campus.� People will be able to pick up their belongings left at the courtyard where the shooting took place early next week, the school said.

Trump, who was joined by Democrats in condemning the violence, said he would award Kirk the Presidential Medal of Freedom, the nation's highest civilian honor. Vice President JD Vance and his wife, Usha, escorted Kirk’s casket to his home state of Arizona aboard Air Force Two on Thursday.

“He wanted to help young people, and he didn’t deserve this,� Trump said Friday. “He was really a good person.�

Tucker and Richer reported from Washington. Associated Press writers Nicholas Riccardi in Denver; Michael Biesecker, Brian Slodysko, Lindsay Whitehurst and Michelle L. Price in Washington; Ty O'Neil in Orem, Utah; Hallie Golden in Seattle; and Meg Kinnard in Chapin, S.C., contributed to this report.