I've certainly heard of accidents in previous years, but nothing this year. Undoubtedly there have been some minor injuries not reported (I once stepped on the hot remnants of a sparkler stick and did some searing of my foot), but I don't think I've ever heard anything on the order of trying to fire a mortor and killing 30 people.
As I said above, Americans can do some damn stupid things - but not quite that bad. Perhaps we should introduce the concept of government-run fireworks to the Afghans so they have less incentive to do this firing of mortors or guns.