The investigation into the suspect accused in the shooting of Charlie Kirk continues, with Utah's Republican Gov. Spencer Cox saying that the person in custody is not cooperating.

Tyler Robinson, 22, is accused of shooting Kirk in the neck during a public appearance at Utah Valley University, Orem, Utah, on Sept. 10.

Cox said on the Sept. 14 edition of ABC News' "This Week" that Robinson was not aiding FBI investigators but that "the people around him are," including a romantic partner with whom he lived.

Cox added that charging documents will detail what authorities believe may have motivated Robinson, as well as forensic evidence linking him to the shooting.

Authorities tied Robinson to the crime through a review of online messages, interviews with his family members and friends, and surveillance video.

“There will be much, much more information on Tuesday, when that document is filed with the courts,” he said.

Here's what we know about Tyler Robinson.

Background of Kirk shooting suspect's family

No potential motive has been officially announced, but family and friends previously told USA TODAY that he had become more political and angry.

USA TODAY previously reported that, as of Sept. 12, the Facebook page for Tyler Robinson's mother was filled with celebrations of her son's milestones and accomplishments. The page appears to depict a tight-knit family where Tyler was the oldest of three sons. The page seems to have been set to private as of Sept. 14.

One of Robinson’s high school classmates, Xander Luke, previously told USA TODAY that he “was politically active and outspoken about people’s rights.” The accused shooter “thought both political sides were contributing to a country being in a worse place and not improving the world,” Luke said.

Robinson, who has no criminal history according to state records, attended high school in the neighboring city of St. George.

He is registered to vote, though he lacks a party affiliation. His parents are registered Republicans.

Tyler wore a Trump-related Halloween costume in 2017, according to Amber Robinson’s Facebook page.

In August 2020, Amber Robinson posted what appears to be an ACT college aptitude test score for Tyler – 34 out of 36 – that would place him in the top 1% of test takers, according to recent averages. He received a $32,000 scholarship to Utah State University, she said.

“We also have to figure out how it came to be that a kid with a 4.0, with a 34 on the ACT, with a full ride scholarship at my alma mater, who didn’t even last a semester, drops out and ends up doing something like this,” Cox said on ABC.

Suspect's romantic partner cooperating, but suspect not cooperating with investigation, Utah gov says

Investigators have been talking with Robinson’s romantic partner, who lived with him, Utah Gov. Spencer Cox said.

“The FBI has confirmed that as well that the roommate was a romantic partner, a male transitioning to female,” he said on CNN’s "State of the Union" Sept. 14. “This partner has been incredibly cooperative, had no idea that this was happening, and is working with investigators right now.”

The governor, when asked about whether Robinson’s partner was linked to a potential motive, expressed caution.

“We’re trying to figure it out. I know everybody wants to know exactly why and point the finger. And I totally get that. I do too,” he said. “I just want to be careful, as I haven’t read all of the interview transcripts.”

Cox added on ABC that Robinson has not confessed to authorities and is "not cooperating."

Inscriptions on bullets found have dual meanings

The FBI recovered what they believe to be the murder weapon, a high-powered bolt-action rifle, and several imprints on the roof where the gunman fired the one fatal shot.

The fired casing, according to Cox, read, “Notices bulges OwO What’s This?” The phrase references an internet meme tied to animated videos and furry culture. OwO references an emoticon, and “what’s this?” denotes cuteness or curiosity, USA TODAY previously reported.

An unfired casing had the inscription “Oh bella ciao, bella ciao, ciao, ciao,” according to Cox. The lyrics reference the anthem of the antifascist Italian resistance during World War II, however Know Your Meme reported that some far-right groups have begun to use the song as an ironic joke.

Luke, the high school classmate, described Robinson as deeply ingrained in internet and meme culture and said the reported engravings on shell casings came as no surprise.

Contributing: Christopher Cann, Nick Penzenstadler, Aysha Bagchi, Dinah Voyles Pulver, Josh Meyer, Will Carless, David DeMille, Michael Loria, Brandon Loomis – USA TODAY

This article originally appeared on USA TODAY: Who is the man accused of killing Charlie Kirk? Here's what to know

Reporting by James Powel and Davis Winkie, USA TODAY / USA TODAY

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