This has been debunked at www.straightdope.com/classics/a950414b.html

Kirby: What goes up must come down
http://www.sltrib.com/food/ci_3485833
By Robert Kirby

On television last week, I watched a demonstration get crazy in a Middle Eastern country. I can't remember which country. It doesn't matter. Pick one.
  The protest was a doozy. Thousands crammed the street chanting and shaking their fists. The mob waved signs, carried banners and set flags alight. Whatever vexed them could apparently be remedied only by promising it death.
  Gunmen in the crowd began blazing away at the sky with automatic weapons. They weren't shooting at anything in particular. It was intended to merely emphasize the level of their annoyance, agreement or even boredom.
  I probably should be interested in whatever touched off the hollering. I never am when the sky-popping starts. I'm too busy hoping the camera will stay on the crowd long enough to see who gets popped when the bullets come back.
  I've always maintained that the size of crowds has an inverse effect on the level of intelligence - the larger the crowd, the lower the collective IQ. A good example of this is when a crowd gets big enough that the people in it forget about gravity.
  Gravity is probably the single most important consideration when shooting at the sky, mainly because there isn't a gun powerful enough in the entire world to shoot a bullet clear into outer space. So whatever gets shot up is coming back down. And it will probably be in a hurry.
  A general rule is that the velocity of bullet coming back to earth will be about the same as when it left the gun. It's going to hurt if you're in the way and not wearing a 500-pound hat.
  In last week's incident, several men pointed their rifles at the sky and let rip the entire magazines. The magazine capacity of the average assault weapon is 30 rounds. Thirty times four (shooters) comes to 120 bullets.

Because gunfire is so much fun, especially when there's a crowd begging to be impressed, let's assume that the shooters couldn't help exhibiting their prowess more than once. The math works out to - what the heck, say, several hundred bullets going up and coming back down at the crowd.
  I'm no ballistics expert but I don't think you have to be one to point out that shooting at the sky above a crowd is just the long version of shooting at the crowd. And if it's a big, densely packed one, odds are that someone in it is going to win the gravity lottery.
  The truly regrettable part is that it won't be the shooters. It's almost impossible to shoot straight up enough that the bullet will come back with a physics lesson only for the person who fired it.
  Nope. It's always some poor slob with nothing to fire at the sky but his indignation who gets killed. Worse, it'll be someone who wanted no part of what's going on: a kid, a guy watching TV, or, heck, even a dog.
  Pity, actually. We wouldn't be in Iraq right now if even one of the bullets Saddam Hussein had fired in the air while trying to show the world how bad he was had come back down and put a skylight in his head.

Is this from a reliable source out of south Flordia?

I cain pick myself up by my hair!

Ya he's full of shit, but we can use his own words to make a larger point:

The math works out to - what the heck, say, several hundred bullets going up and coming back down at the crowd. I'm no ballistics expert but I don't think you have to be one to point out that shooting at the sky above a crowd is just the long version of shooting at the crowd. And if it's a big, densely packed one, odds are that someone in it is going to win the gravity lottery.

Nobody died. So once again, we see that machine guns are no more effective at killing large groups of people than regular firearms.

Quoted: Because gunfire is so much fun...

You have to admit, he's got a valid point here...

Tell the guy to try firing a bullet up at greater than escape velocity and then to measure the velocity when it falls down.

Should keep him busy for a while.

Actually he is full of shit ....... when fired straight up out of a weapon, a bullet comes down faster than when it left the muzzle. Alot of people don't know that.

It's a complicated formula that I won't bore you with, but basically you have to take the energy that the projectile has when it leaves the gun, and then ADD the forces that are contributed by gravity. The density of the air and the Dow Jones industrial average at the exact moment the bullet leaves the muzzle is factored in too. Like I said, it's complicated.

I can't stand it when rookie's talk physics.

Quoted: Actually he is full of shit ....... when fired straight up out of a weapon, a bullet comes down faster than when it left the muzzle. Alot of people don't know that. It's a complicated formula that I won't bore you with, but basically you have to take the energy that the projectile has when it leaves the gun, and then ADD the forces that are contributed by gravity. The density of the air and the Dow Jones industrial average at the exact moment the bullet leaves the muzzle is factored in too. Like I said, it's complicated. I can't stand it when rookie's talk physics.

So, basically, it's Bush's fault.