Kirk assassination suspect formally charged with murder

Prosecutors in the US state of Utah have formally charged a suspect in conservative activist Charlie Kirk's assassination with aggravated murder and intend to seek the death penalty if he is convicted.

Tyler Robinson, 22, is accused of firing the single rifle shot from a rooftop sniper's nest that pierced Kirk's neck last Wednesday on the campus of Utah Valley University in Orem, about 65km south of Salt Lake City.

Utah County District Attorney Jeffrey Gray said at a press conference that his office had filed seven counts against Robinson in all, including obstruction of justice for disposing of evidence and witness tampering for directly his roommate to delete texts.

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".

"The murder of Charlie Kirk is an American tragedy," Gray said in announcing the charges.

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

Authorities have not publicly identified a motive for the killing, although Kirk's wife and other supporters were quick to cast him as a martyr for their cause.

Kirk, the 31-year-old co-founder and head of the conservative student movement Turning Point USA and a key ally of US President Donald Trump, was speaking at an event attended by 3000 people when he was gunned down.

The suspect, a third-year student of an electrical apprenticeship at a state technical college, initially escaped in the pandemonium following the shooting.

He was arrested on Thursday night at his parents' house, about 420km southwest of the crime scene, after relatives and a family friend alerted authorities that Robinson had implicated himself in the shooting, according to Governor Spencer Cox.

Robinson was scheduled to appear via video feed from jail on Tuesday afternoon in Utah County Justice Court in Provo.

Cox said the state would be inclined to seek the death penalty should Robinson be convicted, but that prosecutors would consider the wishes of Kirk's family before making that decision.

Kirk brought young conservatives into politics with Turning Point USA, one of the country's largest political organisations.

He frequently engaged with his critics from the far left to the far right, often inviting members of his audiences to debate him live.

Kirk's shooting raised fears about increasing political violence in a deeply polarised United States.

with AP