Residents posted a flurry of videos on social media, together with theories of aliens or meteors. Others made panicked calls to law enforcement officials.
But not to worry, U.S. military officials said. It was a planned missile test.
The Navy Strategic Systems Programs held a scheduled missile test flight at sea from USS Kentucky, which is a ballistic missile submarine. The test was conducted off the coast of Southern California, the Pentagon said in a statement.
It said the missile was not armed.
"The tests were part of a scheduled, ongoing system evaluation test," the statement said. "Launches are conducted on a frequent, recurring basis to ensure the continued reliability of the system. Each test activity provides valuable information about our systems, thus contributing to assurance in our capabilities."
Fascinated residents shot video of the light.
"At first, it looked like a gold shooting star," witness Matt McKee said.
"It went from gold and small, burning for a few minutes and turned into this blue spot light. Like at an event held at night -- not like shooting out at us, but a white bright light," he said.
"What was weird, the tail was light and wide and it got bluer and bluer. Then it just burned out and went away."
The Los Angeles International Airport issued a statement this week about the military testing.
"The military airspace to the west of LAX will be active for one week, creating traffic route limitations and requiring LAX to temporarily deviate from over-ocean operations," it said.
The military test will continue until November 12.