Utah prosecutors vowed on Tuesday to seek the death penalty for the accused assassin of conservative activist Charlie Kirk and revealed new details of their case, including text messages in which he was alleged to have privately confessed to the fatal shooting.

“I had enough of his hatred,” Tyler Robinson, 22, told his roommate and romantic partner when asked why he had committed the murder, according to transcripts of messages attributed to the suspect in court documents filed by prosecutors.

He is accused of firing the single rifle shot from a rooftop that pierced Kirk’s neck last Wednesday on the campus of Utah Valley University in Orem, about 40 miles (65km) south of Salt Lake City.

The office of Utah County District Attorney Jeffrey Gray charged Robinson with seven criminal counts on Tuesday, including aggravated murder, obstruction of justice for disposing of evidence and witness tampering for asking his roommate to delete incriminating texts.

Some politicians, including US President Donald Trump, have called for capital punishment in the case.

At a press conference, Gray said he had made the decision to seek the death penalty “independently, based solely on the available evidence and circumstances and nature of the crime.”

Robinson made an initial court appearance on Tuesday afternoon via video feed from jail, unshaven and wearing a suicide prevention smock. He remained expressionless but appeared to listen attentively as the judge read the charges and informed him that he could face the death penalty.

The defendant spoke only once, when asked to state his name. Finding Robinson unable to afford legal counsel, Utah Fourth District Judge Tony Graf said he would appoint a defence attorney before the next court hearing, set for September 29.

In the meantime, he was ordered to remain held without bond in the Washington County Jail, where, according to a sheriff’s spokesperson, he has been placed under a “special watch protocol” that includes increased supervision.

Kirk’s killing, captured in graphic video clips that went viral online, sparked denunciations of political violence, opens new tab across the ideological spectrum but also unleashed a wave of partisan blame-casting and concerns that the murder might beget more bloodshed.

In court filings, prosecutors highlighted some of their evidence against Robinson, who was at large for more than 30 hours before eventually turning himself in.

Shortly after the shooting, prosecutors said, Robinson sent a text message telling his roommate to “drop what you’re doing, look under my keyboard.” The roommate, whom officials have also described as Robinson’s romantic partner and transitioning from male to female, then found a physical note from Robinson that read: “I had the opportunity to take out Charlie Kirk and I’m going to take it.”

The roommate then asked Robinson in a text reply, “you weren’t the one who did it right????” Robinson responded: “I am, I’m sorry,” according to a transcript of the alleged dialogue.

When the roommate asked why he had shot Kirk, Robinson wrote back: “I had enough of his hatred. Some hate can’t be negotiated out.” He also asserted he had planned the attack for more than a week, prosecutors said.

In later text messages, Robinson said he wished he had gone back and grabbed the rifle that he left in a bush immediately following the killing, noting it had belonged to his grandfather.

“I’m worried what my old man would do if I didn’t bring back grandpas rifle,” he wrote. “I might have to abandon it and hope they don’t find prints.”

DNA found on the trigger of the alleged murder weapon was linked to Robinson, prosecutors said.

Texts to roommates

Robinson, a third-year trade college student, turned himself the next day, after his parents saw images of the gunman and confronted him, according to the filings. Robinson implied that he wanted to take his own life, but his parents persuaded him to meet them at their home, where Robinson indicated he was the shooter.

Robinson ultimately decided to surrender to police after speaking at his parents’ urging with a family friend who is a retired deputy sheriff, prosecutors said.

“I’m much more worried about you,” he wrote the roommate after revealing he would give himself up. He also urged the roommate to delete the messages and to refuse to speak with police or the media.

The roommate, who was not identified in court papers, is cooperating with authorities, officials have said.

Robinson’s mother told police that over the past year her son had grown more left-leaning and more “pro-gay and trans-rights oriented,” the charging document said.

The relationship with his roommate also led to “discussions” with relatives including his father, who holds “very different political views” from the suspect, according to the document.

Prosecutors added aggravating factors to the murder and firearm charges, alleging Robinson targeted Kirk based on political views and knew children would witness the killing. Under state law, only aggravated murder can carry the death penalty.

Kirk, 31, co-founder of the conservative student movement Turning Point USA and a key Trump ally, was speaking at an event attended by 3,000 people when he was gunned down.

Civil rights advocates have long criticised Kirk for rhetoric disparaging various marginalised groups, including Blacks, Muslims, immigrants, women and transgender people, and for embracing Trump’s unsubstantiated claims of a stolen election in 2020.

Kirk’s supporters describe him as a staunch defender of conservative values and a champion of public debate who galvanised young voters through Turning Point, shaping the MAGA movement’s appeal to Gen Z voters.

Top administration officials have threatened to go after left-wing organisations in the wake of the assassination, which Trump blamed almost immediately on the “radical left.” Critics have expressed concern that Trump may use the killing as a pretext to crack down on his political opponents.

Roughly two out of three Americans believe that harsh rhetoric common in politics is encouraging violence, according to a Reuters/Ipsos poll, opens new tab conducted in the days following Kirk’s murder.