A bright meteor shower.
"We were all just getting up, getting ready to get the day going and all of a sudden we heard a loud bang," says Truckee's Chris Carrillo.
Carrillo had no idea what caused an explosion in the sky on Sunday morning.
"I thought somebody hit the house," says Carrillo.
He wasn't the only one baffled by the boom. Others heard the blast from Winnemuca, to Reno, to Bakersfield. That's when the speculation started.
"My wife came downstairs and asked me, 'What was that' and I said 'I think it was an earthquake," say Mike Armstrong.
"I heard that it was a loud sonic boom," says Jonathan Bradley.
So what really happened here?
Fleishmann Planetarium's Associate Director Dan Ruby says it's likely a very bright meteor called a fireball that fragmented and hit the earth's surface somewhere in a 600 mile radius in the Sierra-Nevada mountains.
"It's rare to see and hear a fireball. this was very clearly heard and the breakup of it was very clearly heard and I'm fairly certain that's what that was," says Ruby.
He believes the fireball happened just after the peak of the annual Lyrid meteor shower.
"I think this is unrelated to the meteor shower, because meteor showers don't produce this kind of thing, but stray rocks in space will be spectacular, and loud, and bright, and look like fire balls across the sky," says Ruby.
So next time you hear a bump in the night, there's a chance it may be a meteor beyond your backyard.