Well you'd use birdshot, obviously. How does the author think people hunt ducks?
It's a lot like the shoot into the water and the bullet streaks through and wounds people. There was a great Mythbusters that debunked that - the water tears apart the bullet within about a foot of the surface. Yet, once again, the myth remains.
There are a few things going on, but most of it, IIRC, stems from the fact that a bullet fired into the air is almost certainly not fired straight into the air, so it retains it's ballistic trajectory and spin. The spin keeps its air resistance relatively low and gravity does not work against the horizontal component of the bullets velocity. The bullet, fired slightly not straight up, will therefore hit you with whatever velocity it got from falling nose first from apogee, combined with whatever velocity sideways it started with (minus some from air resistance).
Bullets fired from a rifled barrel straight up will turn over and tumble at appogee, and their velocity on return will be only terminal velocity of the bullet tumbling through the air. Presumably this case is safe, though potentially painful.
Birdshot is safe I assume because the mass of the individual pellets are low enough so that air resistance is enough to arrest its velocity to something safe. (also the pellets aren't nearly as streamlined as bullets are anyway, though I wouldn't want to be downrange of buckshot fired into the air at an angle...)
That said, some crazy big game hunters use it for long range shots. WAY too much tissue damage for my family's tastes (as it were, what we hunt, we eat), but it is used.
Otherwise imagine all the wasted money they could cause.
Semi-seriously, the two are not mutually exclusive, what's on display, bone, antlers, tusks, fur, etc. is not fit to eat.
Not that I understand the trophy hunting mentality, although the best of them make sure the tasty meat goes to a good home.
[1] like the kind you make for RC dogfighting
