Utah Gov. Spencer Cox confirmed Sunday that the man arrested in the fatal shooting of conservative commentator Charlie Kirk was in a romantic relationship with his roommate, who is transitioning from male to female, and that investigators are probing the relationship as a possible motive.

Tyler Robinson, 22, was taken into custody on Friday after his family alerted authorities to his alleged role in the shooting at an event at Utah Valley University, where Kirk was struck in the neck and later died. Robinson faces charges including aggravated murder, felony discharge of a firearm causing serious bodily harm, and obstruction of justice, and is scheduled to appear in Utah court on Tuesday.

During a Sunday interview with CNN’s Dana Bash, Cox said the suspect’s roommate, identified by officials as Lance Twiggs, was a romantic partner and that investigators are examining whether the relationship factored into the killing. “Yes, definitely. And yes, I can confirm that. I know that has been reported and that the FBI has confirmed that as well, that the roommate was a romantic partner, a male transitioning to female,” Cox said. Cox added that Twiggs has been "incredibly cooperative" and "had no idea that this was happening."

Cox said Robinson has not confessed and is not cooperating with authorities. “He has not confessed to authorities. He is not cooperating, but all the people around him are cooperating. And I think that's very important,” the governor told ABC News.

Investigators said bullets recovered in the case bore engraved phrases and symbols, including references to internet memes and anti-fascist language. According to Cox, one casing was engraved with the phrase “Notices bulge OwO, what’s this?,” a meme sometimes used to mock transgender people and members of the furry community; another read “Hey Fascists! Catch” accompanied by arrow symbols; a third bore the words to the Italian anti-fascist song “Bella Ciao.” A final unfired casing was inscribed, “If you read this you are gay LMAO,” Cox said.

Authorities are also reviewing a note allegedly written by Robinson and messages posted after the shooting. Jud Hoffman, vice president of trust and safety at the social and gaming platform Discord, said Friday there were communications between the suspect’s roommate and a friend in which the roommate recounted the contents of a note the suspect had left elsewhere. Cox said those materials are still being processed for accuracy and verification and could be included in charging documents.

Law enforcement officials have said messages attributed to the suspect on Discord described steps tied to the alleged attack, including retrieving and concealing a rifle and changing outfits. Cox said forensic evidence, shell casings and other materials are being examined as investigators piece together the sequence of events.

Kirk, 31, was speaking at the Utah Valley University event when he was shot. Eyewitness accounts and video show the speaker was addressing a member of the audience who had challenged his comments about transgender people and gun violence just seconds before the gunfire.

Robinson was arrested after being turned in by his family. Utah prosecutors may seek the death penalty; under Utah law a condemned inmate can be executed by firing squad, a method that has drawn public attention in the past. President Donald Trump said he supports seeking the death penalty in the case and described Kirk as “the finest person.”

Kirk’s funeral is scheduled for Sept. 21 at State Farm Stadium in Arizona. Authorities have urged that the investigation be allowed to proceed while they review forensic evidence, digital communications and physical writings to determine motive and culpability.

The investigation remains active. Officials have said they will release charging documents and further details as material is verified and reviewed by prosecutors and the FBI.