Orem (United States) (AFP) - Authorities have taken into custody a person they believe is linked to the killing of Charlie Kirk, a right-wing activist and close ally of Donald Trump, the president himself announced Friday.

Here is what we know so far:

- The shooting -

Kirk, head of the country’s largest conservative youth movement, which he co-founded in 2012 at the age of 18, was speaking around noon Wednesday on the campus of Utah Valley University.

Former Utah congressman Jason Chaffetz, who was at the event, told Fox News that Kirk was responding to a question when a shot rang out.

The 31-year-old collapsed with a neck wound, according to a video clip shot from a nearby location. He was pronounced dead soon after in an announcement by Trump.

Authorities said the killer used a high-powered, bolt-action rifle, firing from the roof of a building up to 200 yards (185 meters) away from his target. They said the killer was lying prone, a position that can increase accuracy.

- Person detained -

Trump announced Friday on Fox News that authorities have apparently taken into custody the main suspect – but he was not definitive.

“We have the person that we think is the person we’re looking for.”

Trump did not identify the person. Law enforcement and local authorities were set to give a press conference shortly in Orem, Utah.

Until Trump’s announcement, delivered on Fox’s popular breakfast news show, police had appeared to be struggling to make a breakthrough.

Late Thursday, officials in Orem held a press conference releasing more details about the suspect’s clothing and initial movements after the shooting, pleading with the public to help identify him.

That may have helped. Trump said that the suspect was turned in by “somebody very close to him.”

Utah Governor Spencer Cox said prosecutors “will pursue the death penalty.”

- The motive -

No official suggestion has been made about the motive.

In a briefing late on Thursday, Cox warned that social media was filling with “a tremendous amount of disinformation.” He said “our adversaries want violence” and cited China and Russia in particular as using bots to spread discord online.

Kirk was a star on the Republican right and a particularly close ally of Trump, helping him to make surging gains in the youth vote when he won election last November.

However, Kirk espoused multiple far-right views, making him hugely controversial for Democrats. He also fell out at times with fellow members of the Republican right – some of them, such as white nationalist leader Nick Fuentes, saying he was not hard-right enough.

The United States has seen repeated political violence over the last decade, including two assassination attempts on Trump – and in addition to a long history of political violence stretching back decades.

- The political reaction -

Politicians on all sides quickly condemned the killing, many of them calling on Americans to heal growing divisions.

Trump’s first reaction on Wednesday was to blame “the radical left.” He toned his rhetoric down on Thursday and said that Kirk had been “an advocate of nonviolence.”

“That’s the way I’d like to see people respond,” he said.

Kirk is being treated as a national hero by the Trump administration.

Trump announced on Thursday he would posthumously decorate Kirk with America’s highest civilian honor, the Medal of Freedom.

The Republican president also told reporters that he would attend Kirk’s funeral.

Kirk’s coffin was transported to his home city of Phoenix on Vice President JD Vance’s official plane.