Tyler Robinson appears to have confessed to murdering Charlie Kirk in an online chat not long getting arrested, reports have indicated.
The message is said to have been sent on the Discord platform from an account belonging to the 22-year-old.
"Hey guys, I have bad news for you all," the message seen by the Washington post read.
"It was me at UVU (University of Utah) yesterday. I'm sorry for all of this."
The message was sent to a private group of about 30 friends last Thursday, about two hours before Robinson turned himself into police.
The day before his message, the chat is said to have featured reactions to the conservative activist's shooting.
"I just saw the video holy shit," one user wrote.
"Bro didn't deserve to go out like that sad."
Tyler Robinson's mug shot
| HANDOUTRobinson did not respond to those messages, sending his own the day after at 7.57pm.
"I'm surrendering through a sheriff friend in a few moments," he said.
"Thanks for all the good times and laughs, you've all been so amazing.
"Thank you all for everything."
Charlie Kirk was speaking at a campus event in Utah when he was killed | REUTERSUS Vice-President JD Vance held a special episode of The Charlie Kirk Show podcast on Monday.
White House Deputy Chief of Staff Stephen Miller vowed to dismantle a "vast domestic terror movement" he claimed was responsible for Mr Kirk's shooting.
Mr Miller said members of the Trump administration would "channel their anger" at the killing of Mr Kirk into dismantling the "organised campaign" behind the murder.
The Deputy Chief of Staff said movement had combined "organised riots, organised street violence, organised campaigns of dehumanisation, vilification, posting people's addresses".
He further said its messaging was "designed to trigger (or) incite violence".
"And the actual organised cells that cary out and facilitate the violence," Mr Miller said.
"With God as my witness, we are going to use every resource we have at the Department of Justice, Homeland security, and throughout this Government, to identify, disrupt, dismantle and destroy these networks, and make America safe again."
Mr Vance said those on the left "are much more likely to defend and celebrate political violence".
Donald Trump is heading to the UK on Tuesday
| REUTERS"This is not a 'both sides' problem," he added.
The comments come as Donald Trump flies to the UK on Tuesday for a state visit.
He will then head back to Arizona on Sunday to attend Mr Kirk's memorial service.
Mr Trump vowed to "say a few words" at the service.
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