Tyler Robinson, 22, left a note under a keyboard for his roommate to discover, said Utah County Attorney Jeffrey Gray. He added that the roommate was Mr. Robinson's romantic partner.
According to Mr. Gray, the note said: I had the opportunity to take out Charlie Kirk, and I'm going to take it. The prosecutor also shared text messages between the roommates, including one in which the defendant allegedly said he shot Kirk because he had had enough of his hatred.
The suspect is being held without bail in a special housing unit at the Utah County Jail. He made his first court appearance on Tuesday, appearing remotely as prosecutors read the seven charges against him, which include aggravated murder and other serious offenses.
They are also pursuing the death penalty over Kirk's shooting, which occurred while he was speaking at Utah Valley University.
The prosecutor unveiled a trove of evidence at a news conference, including the defendant's alleged confession and DNA found on the trigger of the rifle suspected to have been used in the crime.