There was an accident at a fireworks show on the Fourth of July in Simi Valley, California.  Some fireworks exploded somehow, and then the rest started shooting off into the crowd.  At least 35 people were injured.  They think the platform that was holding the fireworks collapsed, and the ones that were left went off at an angle, right toward where most of the people were watching.  Here's an amateur video that shows a good angle of it.