A 71-year-old man, who was arrested shortly after the assassination of Charlie Kirk and then released, tried to help the suspected gunman escape by faking a confession, authorities say.

Utah County Sheriff Michael Smith said George Zinn admitted to police that he had “yelled that he was the shooter to allow the actual suspect to flee”.

The prime suspect in the killing is 22-year-old Tyler Robinson, who appeared to acknowledge Mr Zinn’s initial arrest after the shooting, telling his roommate over text that the police “grabbed some crazy old dude”.

Mr Zinn is being held on obstruction of justice charges. Separately, he has also been charged with possession of child sex abuse material.

George Zinn was one of two people that the police had detained for questioning after conservative commentator Charlie Kirk was fatally shot at Utah Valley University on 10 September.

Police later determined that the two suspects were not involved in the killing.

Mr Zinn “intentionally yelled he was the shooter and by doing so, obstructed Law Enforcement from focusing on the actual shooter”, the sheriff said in a statement.

Court documents filed by campus police allege that Mr Zinn began shouting: “I shot him – now shoot me.”

When asked by an officer where the weapon used in the shooting was located, he allegedly responded: “I am not going to tell you”, according to the documents.

The sheriff said that there was currently no evidence Mr Zinn colluded with the gunman.

Sherriff Smith added that Mr Zinn is also being held for the sexual exploitation of a minor, and that agents found more than 20 images of children “in various stages of undress and sexual posing”.

On Monday, a judge ordered that Mr Zinn be held without bail, calling him a “substantial danger” to the community.

It was not clear from court records if he had a lawyer.

Mr Zinn is well known among organisers of public events in Salt Lake City, the New York Times reported. “He showed up frequently to public forums with the intention to disrupt the event or question a high-profile speaker,” it said.

He also has a long history of minor crimes, including an arrest in 2013 for sending a threatening email to the hosts of the Salt Lake City Marathon just days after the Boston Marathon bombing, the newspaper wrote.

Robinson, the prime suspect in the killing was charged on seven counts including aggravated murder, on Tuesday.

Charlie Kirk was one of the highest profile conservative activists and media personalities in the US.

Known for his outspoken views on gender, race, and gun rights, Kirk was a polarising figure and a close ally of President Donald Trump.

He was shot while hosting an event at Utah Valley University, in what authorities have described as a targeted attack. President Trump called Mr Kirk “a patriot” and said his killing marked a “dark moment for America”.