The noise woke people up in Foothill Ranch at about 12:15 a.m. Around the same time, a security camera captured a bright light, and with the flash came a huge boom.
"Like a bomb or an explosion. I was freaking out, I was shaking," said Caitlin Heinly of Foothill Ranch.
The explosion set off car alarms and rattled windows.
"I thought maybe a meth lab blew up, but then I started thinking maybe it was a meteor or something like that," said Serena Abid.
The Orange County Sheriff's Department said it received several calls. Officers responded, but after investigating from the ground and air, authorities say nothing was located.
The boom remains a mystery, leading to more speculation. Could it be a meteorite that landed in the nearby canyon?
Bomb experts scoured the neighborhood in the morning after getting a call from Nick Krueger's parents, who found pieces of what looked like cardboard in their backyard.
The sheriff's department says the evidence points less to a meteorite and more to illegal fireworks.