What goes up must come down and that includes bullets. Shooting guns into the air be it for celebration or part of a Wild West showdown is quite a dangerous act despite what the movies show.
Bullets fall back to the ground with much slower speeds than their muzzle velocities, but nevertheless they can still fall fast enough to penetrate skin and bone. And when something falls from above one of the prime targets it might land on is someone's head. Property damage in the form of shattered windows or holes in roofs is another result.
This is very common in areas like the Middle East, but it's also an ill-practiced tradition by some in the United States particularly on New Year's Eve and 4th of July when thousands of people take their guns to the skies. I had a lot of trouble finding good statistics on exactly how many people are injured or die from falling bullets worldwide, but it seems like there's around a couple hundred known cases a year.
So please don't shoot into the air. It takes a fluke for your bullet to kill someone, but if it does that is murder.