Officials have identified the person accused of fatally shooting conservative activist Charlie Kirk as 22-year-old Utah resident Tyler Robinson.
His killing launched a multi-day manhunt among local, state and federal authorities.
According to Cox, investigators interviewed a family member of Robinson's who said he had "become more political in recent years.".
Images released by the FBI show a person of interest in the shooting of Charlie Kirk.
Kirk's killing has prompted national outrage in recent days and renewed fears over political violence in the United States.
"This is certainly about the the tragic death, assassination, political assassination of Charlie Kirk," Cox, a Republican, said.
Turning Point USA has not publicly commented on the arrest or the identification of the suspect. »