Star-Spangled Banners flew as fans gathered on Huntington Beach for a memorial honouring Charlie Kirk.

Footage shows a large crowd singing the national anthem together, many carrying American flags as they paid tribute to the slain Trump ally and conservative commentator.

Charlie, who cofounded Turning Point USA, was killed by a suspected sniper at around 12:25 pm on Wednesday last week while he held a political discussion at a campus event at Utah Valley University.

President Donald Trump said he is 'filled with grief and anger at the heinous assassination' and called it a 'dark moment for America'.

Law enforcement has taken a suspect into custody, with Utah Governor Spencer Cox identifying the alleged shooter as 22-year-old Tyler Robinson.

Governor Cox said: 'He is not cooperating, but all the people around him were cooperating, and I think that's very important.'

Robinson has been formally charged with aggravated murder and six other offences, including obstruction of justice and witness tampering.

Prosecutors are also seeking the death penalty for the accused killer.