The officers thought their lives were threatened, he said, "and more importantly, they thought the lives of others were in jeopardy."
The theater's manager told Krongard the shooting occurred during a screening of "Les Miserables."
A moviegoer told KGTV the lights suddenly went on during the film and two officers came into the theater with their guns. Another witness told the station that everyone got on the floor and started heading for the exit doors.
McManus said the gunman never made any threats to others in the theater. He said the man had left a suicide note at his Escondido home before going to his girlfriend's workplace to confront her.
It was the second shooting at a San Diego County movie theater in as many days.
A concession worker suffered an arm injury when a shot fired outside a San Marcos movie theater went through the lobby window and struck her, sheriff's officials said.
The shooting occurred during a fight in the parking lot at Edwards San Marcos Stadium 18 and triggered a large police response because authorities were initially not sure whether there was a shooter inside the Cineplex.
No arrests have been reported after the San Marcos shooting.