PROVO, Utah, Sept 15 (Reuters) - The suspect accused of assassinating right-wing activist Charlie Kirk in Utah wrote a text message before the shooting that he planned to kill Kirk, FBI Director Kash Patel said on Monday.

In an appearance on Fox News'"Fox & Friends," Patel said investigators believe Tyler Robinson also wrote a physical note saying he had the "opportunity to take out Charlie Kirk" and would do so. The note was destroyed, Patel said, but investigators have collected forensic evidence that it had existed and confirmed its contents through interviews.

Patel did not say who had received the text message or whether anyone had seen the written note before the attack.

Investigators have not publicly identified a motive. Law enforcement authorities have said they believeRobinson acted alone when he shot Kirk but are investigating whether anyone else had a role in plotting the killing.

Separately, the Washington Post reported on Monday that Robinson had sent a message via the online platform Discord to friends apparently confessing to the crime on Thursday night, shortly before he was arrested.

"It was me at UVU yesterday. im sorry for all of this," read a message from the account belonging to Robinson, the newspaper reported, citing two people familiar with the chat as well as screenshots it had obtained.

Kirk, an influential ally of U.S. President Donald Trump who co-founded the leading conservative student group Turning Point USA, was killed by a single rifle shot last Wednesday during an event at Utah Valley University in Orem, about 40 miles south (65 km) of Salt Lake City.

COURT HEARING BY VIDEO

Robinson, 22, is expected to be formally charged on Tuesday, around the same time that he makes an initial court appearance by video from his jail cell.

Patel told Fox News that DNA matching the suspect's was found on a towel that was wrapped around the rifle believed to be the murder weapon and on a screwdriver found on the rooftop that served as the shooter's sniper perch.

Robinson has not cooperated with authorities, Utah Governor Spencer Cox said on Sunday, but investigators have been interviewing his friends and family in an effort to determine the motive for the shooting.

The killing has shaken a country already gripped by a spike in political violence, fueled by deepening polarization between the right and the left.

Both sides have universally condemned Kirk's slaying as an indefensible act of political violence, though partisan differences have emerged over the framing of that message.

Some Republicans, including Trump, have blamed liberal groups for Kirk's murder despite a lack of evidence, while Democrats have noted that left-wing figures have also been the targets of political violence in recent years.

The left and right also disagree over Kirk's legacy and how he should be remembered.

LEGACY DIVIDED

Kirk's supporters cast him as an influential and charismatic figure who galvanized support for Trump among younger voters in 2024, and the Republican president has honored Kirk by ordering flags flown at half staff on public buildings.

Civil rights advocates and liberals have criticized Kirk as a divisive figure who embraced Trump's unsubstantiated claims of a stolen election in 2020 and has marginalized Blacks, women, the LGBT community, Muslims and immigrants with derogatory rhetoric.

In an appearance on Kirk's eponymous podcast on Monday, Vice President JD Vance said the"incredibly destructive movement of left-wing extremism" had helped lead to Kirk's killing.

While Robinson was raised in a Mormon household by religious parents in a deeply conservative region of the state,"his ideology was very different than his family," Cox said on Sunday on NBC's "Meet the Press" program, without going into specifics.

State records show Robinson had registered to vote without choosing a party affiliation and did not vote in the 2024 presidential election. But a relative told police that Robinson had grown more political and had expressed dislike for Kirk in a recent conversation.

House Speaker Mike Johnson and three other top members of the House Republican leadership held a brief vigil on Monday for Kirk, attended by dozens of lawmakers, friends and supporters in Statuary Hall of the U.S. Capitol.

Back in Utah, at the scene of Kirk's assassination, scores of mourners have flocked to makeshift memorials in recent days to leave flowers and handwritten notes, and to inscribe messages in chalk on campus sidewalks, many of them Bible verses.

Dally Bronson, 22, a sheriff's dispatcher from neighboring Wasatch County who was on duty at the time Kirk was shot, said that as a devout Christian she felt torn about what justice should look like.

Describing herself as an admirer of Kirk, Bronson said she had been praying for both him and his accused killer.

"By all accounts (Robinson) was a good kid until recently, when something went terribly wrong," she said, speaking through tears. Kirk's"killing isn't about one political side or the other - it's about good and evil. The shooter encountered a darkness online, he went into some black hole on the internet, and it's something people our age fall into."