With images like these, it’s no wonder California — not to mention the Twittersphere — freaked out Saturday evening when an unannounced test  of a submarine-launched Trident missile lit up the evening sky.

Photographer Porter Tinsley  and her wife were on the shore of California’s desolate Salton Sea taking long exposures and time lapses with three different cameras when they witnessed what they thought at the time was a chemical or nuclear weapon detonating over Los Angeles two and a half hours to the west.

“We thought everyone in L.A. was going to die,” said Tinsley, whose blog has even more photos.

Fat chance. The pyrotechnics Tinsley and thousands of other casual skywatchers observed Saturday were due to the first of two Trident 2 D5 missiles with dummy warheads the U.S. Navy test fired between Saturday evening and Monday afternoon. The big, bright flash some mistook Saturday for a detonation,  missile intercept or UFO  is actually the result of the solid-fueled Trident missile jettisoning one of its three stages.

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photos courtesy of Porter Tinsley

In a statement issued Monday night, U.S. Navy Adm. Ceil Haney, head of Strategic Command, described Saturday’s test  flight — one of 156 such tests since  1989 of the Lockheed Martin-built strategic “demonstrate[s] the readiness of our nation’s nuclear triad and serve to assure our allies and deter our potential adversaries.”