A dead 11 y.o. young boy outside a school and a now 95% paralyzed 7 y.o. girl are two examples off the top of my head which happened in Greece within the last five years. The bullets fell on the upper part of their heads. In the latter case, the mother said she heard a sound similar to piercing an egg's shell. In the latter case the murderer was actually found.

Fair enough. They do cover the lethality of falling bullets. They seem to be fairly deadly. Most falling with enough force to pierce the skull. I'm not sure about their methodology.

Their methodology is probably off because it doesn't seem to account for bullets tumbling. Bullets spin and that spin keeps the pointy end forward. If they're fired straight up and then fall back down they're going to end up tumbling. That makes their air resistance much higher and therefore much slower. It will also reduce the severity of impact. Instead of getting hit by the pointy end you're probably going to be hit by a bigger surface area.