“Air raid sirens were sounded throughout Los Angeles County at 2:25 a.m. and a total blackout was ordered. Thousands of air raid wardens were summoned to their positions. At 3:16 a.m. on February 25, the 37th Coast Artillery Brigade began firing 12.8-pound anti-aircraft shells into the air at the object(s); over 1400 shells would eventually be fired [1]. Pilots of the 4th Interceptor Command were alerted but their aircraft remained grounded. The artillery fire continued sporadically until 4:14 a.m. The objects were said to have taken about 20 minutes to have moved from over Santa Monica to above Long Beach. The "all clear" was sounded and the blackout order lifted at 7:21 a.m.”
The famous 25 February 1942 “Battle of Los Angeles” photo