Cops are understood to be probing the possibility Charlie Kirk’s suspected killer had an accomplice.

FBI agents are investigating footage which allegedly shows suspected gunman Tyler Robinson on a doorbell camera talking about the shooting moments after the assassination.

Questions are now reportedly being asked as to whether Robinson, 22, had someone help him or who knew about the killing but remained silent.

Detectives interviewed a family on Thursday afternoon who lived in the neighbourhood next to the university campus who handed over the footage.

The Sun reports it shows a man walking past the house - which backs onto a wood - talking into a mobile phone about the shooting just minutes after it happened.

A police probe is now understood to be underway to look into if the man is Robinson.

Officials had said in an earlier press conference that they believe the shooter acted alone but that all lines of enquiry are ongoing.

Who is Kirk’s accused killer Tyler Robinson?

Robinson was a student who lived at home with his parents in the city of St George, Utah, where he grew up, according to reports.

Authorities announced on Friday that Robinson, 22, had been arrested and identified as the suspected shooter of the conservative influencer.

He has no criminal history, according to state records.

He was a third-year student in an electrical apprenticeship program at Dixie Technical College.

Robinson also earned college credits through Utah Tech University from 2019-2021, while he was in high school, a spokesperson from Utah Valley University, where Charlie Kirk was shot dead Wednesday, told NBC News.

Photos on social media depict Robinson - who is the oldest of three sons - with a tight-knit family on vacations and fishing trips.

In August 2020, his mother Amber Robinson posted what appears to be an ACT college aptitude test score for Tyler – 34 out of 36 – that would place him in the top 1% of test takers, according to recent averages.

Utah Governor Spencer Cox told reporters that Robinson allegedly “confessed” to family members that he was responsible for Kirk’s death.

“On the evening of September 11th, a family member of Tyler Robinson reached out to a family friend, who contacted the Washington County sheriff’s office with information that Robinson had confessed to them or implied that he had committed the incident,” he said.

US President Donald Trump said Kirk’s father had turned his son into police after first taking him to see a minister. The suspect’s father is a retired veteran law enforcement officer, according to reports.

Mr Cox told reporters that investigators had interviewed a family member who said the suspect had become more political in recent years.

Mr Cox relayed the account of a relative, who said that during a family dinner prior to the shooting, Robinson had mentioned that Mr Kirk was coming to Utah Valley University and raged that the activist “was full of hate and spreading hate”.

“The family member referenced a recent incident in which Robinson came to dinner prior to September 10, and in the conversation with another family member, Robinson mentioned Charlie Kirk was coming to UVU,” Mr Cox said.

“They talked about why they didn’t like him and the viewpoints that he had.”

Mr Cox said investigators had also spoken to a roommate of the suspect who had shown them messages with an account named “Tyler” on the messaging app Discord.

The messages referred to a need to retrieve a rifle from “a drop point” and the rifle being left in a bush, wrapped in a towel.

Investigators believe the alleged gunman acted alone and “do not at this time have any information that would lead to any additional arrests.”

Robinson had received a US$35,000 (A$52,000) academic scholarship to Utah State University in Logan, a now viral video where he reads a letter aloud reveals.

However, he only attended the school for one semester in 2021, a school spokesperson told NBC News. It is a separate institution from the one where Kirk was murdered.

Robinson was raised Mormon, and yet fired his fatal shot just moments after the conservative influencer had spoken in glowing praise of the Church of Latter Day Saints, The NY Post reports.

Footage from Kirk’s final event at Utah Valley University on Wednesday shows him bantering with a member of the Mormon faith in the crowd, referring to him as the “guy in the shirt and tie at the front here,” before going on to speak of his love for the church.

“I love how Mormons send missionaries around the world, I love how polite they are. … Half my team is Mormon,” he said, to huge cheers from the Utah crowd.

“Mormons are great people. Let me just say, I’m an evangelical Christian, but I’m not one of those guys that hates on Mormons,” he added.

Kirk’s words came just minutes before he was shot and killed — allegedly by Robinson — whose neighbour said he attended the Church of Jesus Christ of Latter-Day Saints in St. George, Utah.

“He went to our church when he was younger,” a neighbour told the publication.

Kirk’s hard line views on race, gender, gun ownership and what many said was his antisemitism made him an intensely divisive figure, although even opponents praised his willingness to debate.

While authorities said they did not know the motive, Mr Cox noted that anti-fascist slogans were inscribed on two of the unused bullet casings.

One cartridge had written on it, “Hey, fascist! Catch!”, and another featured “Bella ciao,” apparently a reference to a World War II-era Italian anti-fascist song, said Utah Governor Spencer Cox

Other cartridges were marked with symbols and wording that appeared to be from the online gaming culture.