A bullet expends its kinetic energy via air friction. Unless it richochets off the drone, it'll fall harmlessly some miles away.
The reports of 'celebratory gunfire' deaths are all necessarily speculative - the angle of the shot is impossible to measure. We can resort to physics to get a better answer than that derived from headlines.
A close friend of mine was killed by a stray bullet this year at a 4th of July celebration. She was in a crowd of thousands of people gathered to watch some local fireworks. The shooter was miles away and probably has no idea that they murdered someone.
http://statenews.com/index.php/article/2012/07/student_shot_...