Humans.
If they're not racing, polluting, protesting, getting drunk, playing "Wargames"(real, drills or the A.I videogame) or making asses of themselves, they're off joining the KKK and they're
inadvertantly shooting someone else even though they fired into the empty sky in the opposite direction.
Honestly, these misanthropes should be entered into the
Darwin Awards for their complete lack of intelligence, Artificial or Natural.
Still, it answers the question:
"Can bullets still injure people if they're fired skyward?"
Yes little Billy, because as we all know, what must shoot up, must shatter bone, blood and tissue coming down!