Hundreds of residents called 911 after seeing strange lights in the sky just after dusk. A flash of white light streaked across the night sky. Some thought it was a UFO that would finally prove the existence of alien life. But, after countless calls, law enforcement informed citizens what they had actually viewed was a SpaceX rocket.

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California and Arizona residents were astonished as they looked upwards into the sky last Friday night. Television and radio stations received calls from people describing what they had witnessed.

Cars pulled to the side on the freeway, while others stopped at red lights to take pictures of the spectacle. Over 130 people in Los Angeles called 911 in a span of 20 minutes.

The notion of a visit from an alien presence quickly shifted to something more sinister — a possible North Korea nuclear missile heading to the U.S. Elon Musk, the CEO of SpaceX decided to have some fun at the expense of concerned citizens on Twitter where he wrote: “nuclear alien UFO from North Korea.”

Eventually those concerned about the lights were told it was the final launch for SpaceX, the Falcon 9 booster, a reusable rocket, lifting off from the coastal Vandenberg Air Force Base.

Relieved, Twitter sounded off to set everyone’s mind at ease. One Twitter user wrote, “#SpaceX gotta give a better Public notice… I aint know if this was a Rocket, aliens, Santa Claus, or North Korea.”

Another user wrote: “Big thanks to Elon Musk and SpaceX for the hilarious alien debate that ensued between my family once we saw your rocket in the sky tonight.” Elon Musk responded and continued to show his outgoing personality. “It was definitely aliens,” he wrote.

SpaceX is expected to have four more launches by mid-2018, according to the Daily Mail. Musk recently revealed a giant rocket that he plans to send to Mars in the coming years.

At least people were good sports about it after they discovered what the lights were. We could have ended up with a real-life Orson Well’s “War of the Worlds” incident.

This content was originally published here.