The arrest of 22 year old Tyler Robinson, marks a major break in a case that shocked the country and raised fresh alarms about political violence in a deeply polarised United States.
Robinson is believed to have acted alone, and the investigation is ongoing, Utah's Republican Governor Spencer Cox said. He was arrested on suspicion of capital murder, weapons and obstruction offences and is expected to be formally charged on Tuesday ahead of an initial court appearance.
On Friday, Kirk's widow, Erika, gave her first public remarks since the shooting. Speaking from the office where her late husband hosted his podcast, she said he loved America, nature and the Chicago Cubs.
"But most of all, Charlie loved his children and he loved me with all of his heart," she said.
She had a pointed message for "the evildoers responsible for my husband's assassination," though she did not specifically name Robinson.
"You have no idea the fire that you have ignited within this wife. The cries of this widow will echo around the world like a battle cry," she said.
She thanked Trump, saying through tears that her husband loved the president, and vowed to keep her husband's work alive, continuing his campus tour, radio show and podcast.
Robinson's arrest capped a frenetic day-and-a-half search that had authorities pleading for tips and leads from the public.
We got him," Cox told reporters at a briefing on Friday, giving credit to Robinson's family in helping turn him over to authorities.
The assassination while Kirk was speaking at a Utah campus was condemned on all sides of politics, but has deepened divisions, as well as sparking pleas for differences to be resolved without violence.
Authorities described evidence they said shed potential light on the slaying.
That included the engravings on bullet casings, including one that said, "Hey, fascist! Catch!" Cox said.
The clothes the suspect wore when confronted by law enforcement matched what he had on when he arrived on campus, and a family member confirmed he drove a grey Dodge Challenger like the one seen in a surveillance video, Cox said.
Robinson's father recognised 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 an official. His father contacted their youth pastor, who also occasionally works with the US 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. However, he attended for only one semester in 2021, a spokesperson said.
Robinson currently is enrolled in an electrical apprenticeship program at Dixie Technical College near his hometown, in southern Utah.
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.
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.
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.
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 honour.
