Officers using a stun gun subdued the suspected gunman, identified as Ryan Elliot Giroux, 41, at a vacant condominium where he had taken refuge, some four hours after the initial shooting, Mesa police spokesman Esteban Flores told reporters.

"At this time we believe he is responsible for each and every one of these shootings," Flores said. Police said the motive for the rampage was still unclear but that the initial gunfire erupted following an argument at the motel.

By Wednesday evening, police were serving multiple search warrants at several locations, Flores said.

He said Giroux had been "asking for something in particular," but that police did not know if it was drugs.