But late Tuesday night, the U.S. Strategic Command says the object was likely a Russian rocket booster reentering the atmosphere.
Still, there's been a lot of speculation about what it was.
"I looked up in the sky and I saw this streak across the sky. It looked almost like a firework. But it looked way too high up and it was going way too fast to be a firework," Berkeley resident Armando Epifani said.
"We had a meteor shower a week and a half ago, the Geminid meteor shower. The Geminids are small particles and they have very short arcs when they come down through the sky," Chabot Space & Science astronomer Gerald McKeegan said.
After the bright light streaked across the sky, people lit up social media with videos and pictures of that fireball.
If you took photos or videos of the mysterious light, tag your photos and videos on Twitter, Instagram, or Facebook with #abc7now.