Falling bullets
Falling bullets are a potentially fatal hazard that occur mainly due to celebratory gunfire. Bullets are very dense metallic objects, and when fired high into the air they acquire enough potential energy that they can come down with great force. Several people have been killed by them, including a four year old boy at church.
Most firearms training requires shooters to know where their bullet is going from the gun to the target and to ensure that it will wind up in a safe place (such as the earth) if it misses the target. One should never fire a gun randomly into the air.