The suspect in Charlie Kirk’s shooting, Tyler Robinson, is a 22-year-old native of Utah who authorities say had allegedly criticised the conservative influencer in a recent conversation and was living with his family.

Robinson was arrested late on Thursday after a family friend called authorities, officials said on Friday.

Investigators have not publicly identified a motive. Utah governor Spencer Cox told reporters that a family member interviewed by law enforcement said Robinson had recently mentioned Kirk’s appearance at Utah Valley University, where he was shot on Tuesday, at a recent dinner.

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“They talked about why they didn’t like him and the viewpoints he had,” Cox said. Robinson had also become more political in recent years, the family member told investigators.

Robinson does not appear to have any criminal history. He was a registered voter but was not affiliated with a political party, according to state voter records.

Records show he was an “inactive” voter, which means he had not cast a ballot in recent elections and had not responded to a mailing from the county clerk’s office.

Other details about Robinson’s life were still emerging on Friday.

He briefly attended Utah State University in Logan for one semester in 2021. It was not clear why he left the college.

A Utah Valley University representative confirmed that he is a third-year student in the electrical apprenticeship programme at Dixie Technical College, located in the south of the state, more than three hours from UVU, where the shooting took place.

A memorial for Charlie Kirk at the Turning Point USA headquarters in Phoenix, Arizona. Photograph: Eric Thayer/Getty ImagesA memorial for Charlie Kirk at the Turning Point USA headquarters in Phoenix, Arizona. Photograph: Eric Thayer/Getty Images

In a video posted by his mother on Facebook, Robinson can be seen reading aloud from a letter offering him a four-year scholarship from Utah State University, as she cheered. Another post said Robinson had earned a score of 34 on the ACT college entrance exam, which would put him in the top 1 per cent of test takers, according to the Princeton Review test preparation company.

At the time of his arrest, he was living at his family’s home in Washington county, in the southwest corner of Utah near the Nevada border, Cox said.

He has two younger brothers, according to his parents’ Facebook posts. His mother is a social worker at a non-profit healthcare company, while his father’s occupation was not immediately clear.

His mother’s Facebook posts over the years – most of which were deleted on Friday – mostly doted on her family: documenting trips to Alaska, the Caribbean and Disneyland; celebrating school plays, Halloween costumes and adopted pet rabbits; expressing pride as the three boys moved up in school. None of the posts appeared political in any way.

Other posts show Robinson and his brothers occasionally with guns, though that is not uncommon in a state with permissive firearms laws.

“Driving away without him was one of the most difficult things I’ve had to do in a long time,” his mother wrote in one post about helping him move to college in 2021. “He’s so excited to start his journey and it’s going to be so amazing for him!”

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On Thursday evening, Cox said, a family member called a family friend who in turn called the Washington county’s sheriff’s office “with information that Robinson had confessed to them or implied that he had committed the incident”.

Robinson’s roommate also showed messages Robinson had sent describing leaving a rifle in a bush wrapped in a towel – matching the weapon that authorities recovered in a wooded area near the scene of the shooting.

Robinson was booked into the Utah county jail in Spanish Fork, about 19km south of the university where Kirk was shot. He had not been formally charged on Friday evening.

Kristin Schwiermann (66), a neighbour of the Robinson family, said Robinson was “very respectful and quiet” and “had friends”.

“He was smart,” she said, and “aced his ACTs and got a full ride at university.”

“He’s from a very loving family,” she said.

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The news shocked her, she said: “I didn’t think he would have done this.”

Many of the messages on the bullet casings allegedly used or carried by Robinson adopt the flippant, sarcastic, in-jokey chatter often found on online message boards and in-game chats.

“Up arrow, right arrow, and three down arrow symbols,” as the governor described one engraving, appears to be a reference to a sequence of controller moves that unleashes bombs in the popular video game Helldivers 2.

Another phrase on the cartridges, “Notices bulges OwO what’s this?” is used for trolling, with roots in online role-play communities.

Some of the other messages on the unfired cartridges are more straightforward, including one that says: “Hey, fascist! Catch!”

Another featured the words “Bella ciao”, an apparent reference to an Italian song adopted by the anti-fascist resistance during the second World War. It is still sung by the Italian left and in other countries to commemorate the fight against fascism. – Reuters/Guardian