Washington: The man arrested in the killing of right-wing activist Charlie Kirk is not cooperating with authorities, but investigators are working to establish a motive for the shooting by talking to his friends and family, Utah Governor Spencer Cox said on Sunday (Monday AEDT).

Cox said the accused gunman, Tyler Robinson, 22, would be formally charged on Tuesday. He remains in custody in Utah.

Investigators have yet to piece together why Robinson allegedly scaled a rooftop at Utah Valley University during an outdoor event and shot Kirk in the neck at long range on Wednesday.

A memorial for Turning Point USA CEO and co-founder Charlie Kirk in Utah. Credit: AP

Kirk, a staunch ally of President Donald Trump and co-founder of the conservative student group Turning Point USA, was kill

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