The man accused of assassinating conservative activist Charlie Kirk was charged on Tuesday with aggravated murder.

The charge means Tyler Robinson (22) could face the death penalty if convicted of killing Mr Kirk last week.

Announcing the charges, Utah County Attorney Jeff Gray said: “The murder of Charlie Kirk is an American tragedy.”

Mr Kirk was shot on September 10th as he held a speaking engagement before students at a university in Utah, and died soon after.

Prosecutors allege Mr Robinson shot Mr Kirk in the neck with a bolt-action rifle from the roof of a nearby campus building.

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Mr Robinson was also charged with felony discharge of a firearm, which is punishable by up to life in prison, and obstructing justice, punishable by up to 15 years in prison.

He was scheduled to appear on camera for a virtual court hearing on Tuesday afternoon.

It was unclear whether Mr Robinson had a lawyer who could speak on his behalf. His family has declined to comment.

Mr Robinson was arrested late on Thursday near St George, the southern Utah community where he grew up.

Investigators have spoken to his relatives and carried out a search warrant at his family’s home in Washington, Utah, about 390km southwest of where the shooting happened.

Mr Kirk, a dominant figure in conservative politics, became a confidant of president Donald Trump after founding one of the country’s largest political organisations, Turning Point USA.

He brought young, conservative evangelical Christians into politics. His shooting raised fears about increasing political violence in a deeply polarised United States.

While authorities say Mr Robinson has not been co-operating with investigators, they say his family and friends have been talking.

Utah governor Spencer Cox said those who know Mr Robinson say his politics shifted left in recent years and he spent a lot of time in the “dark corners of the internet”.

FBI director Kash Patel said told Fox News Channel show Fox & Friends that DNA evidence has linked Mr Robinson to a towel wrapped around a rifle found near the Utah Valley campus and a screwdriver recovered from the rooftop where the fatal shot was fired.

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Before the shooting, Mr Robinson had written a note that he had an opportunity to take out Mr Kirk and was going to do it, according to Mr Patel.

The FBI also is looking at “anyone and everyone” who was involved in a gaming chatroom on the social media platform Discord with Mr Robinson, Mr Patel said on Tuesday during a Senate Judiciary Committee hearing in Washington.

The chatroom involved “a lot more” than 20 people, he said.

“We are investigating Charlie’s assassination fully and completely and running out every lead related to any allegation of broader violence,” Mr Patel said in response to a question about whether the shooting was being treated as part of a broader trend of violence against religious groups.

Investigators are working on finding a motive for the attack, Mr Cox said on Sunday. He said Mr Robinson’s romantic partner was transgender, which some politicians have pointed to as a sign the suspect targeted Mr Kirk for his anti-transgender views.

But authorities have not said whether they had evidence that that played a role.

Mr Kirk was shot while taking a question that touched on mass shootings, gun violence and transgender people.

Utah Department of Public Safety commissioner Beau Mason said that Mr Robinson’s partner has been co-operative.

He said investigators believe Mr Robinson acted alone during the shooting, but they also are looking at whether anyone knew of his plans beforehand.

In the days since Mr Kirk’s assassination, Americans have found themselves facing questions about rising political violence, the deep divisions in the US and whether anything can change.

Despite calls for greater civility, some who opposed Mr Kirk’s provocative statements about gender, race and politics have criticised him since his death.

Many Republicans have led a push to punish anyone they believe exulted in his death, causing both public and private workers to lose their jobs or face other consequences at work.