Meteors like these aren't wholly uncommon (4,589 in 2011), but they sure are unpredictable. I was lucky enough to see one when I was driving home one night in Tallahassee. We call them "fireballs." They streak across the sky and explode just like these. Scared the shit out of me. No sonic boom though. I guess these were much lower. Apparently, there is another term, "bolide," which can have a few different meanings, one being a fireball which makes an audible sound (like the sonic boom) as it enters the atmosphere, or a meteor which explodes.