US President Donald Trump has announced that the suspected killer of Charlie Kirk has been taken into custody.

“I think we have him,” Trump said. "With a high degree of certainty, we have him in custody."

Speaking to Fox News, the US president said: "Somebody very close to him turned him in."

He then shared further details on how that person went to the suspect's father, who then went to a US Marshal, the BBC reports.

"The father convinced the son [to turn himself in]," Trump said.

Trump also said the suspect is aged "28 or 29" – authorities previously said the suspect appeared to be collage age.