They heard it, felt it, and a couple of people even said a "loud boom" rattled their homes in West Valley, but an explanation on a cause for the boom was a bust
Sonic boom from a jet would be my guess. When I was a kid I lived near an air force base and sometimes a plane would go by at supersonic speed at low-ish altitude. It literally felt, and sounded, like a huge explosion. Windows rattling, ears ringing, all of that.