Iraq is not a safe place like some people want ma make it look like. It is a very dangerous place, there are terrorist attacks periodically. The US patrollers that shot the italian convoy putting about 300 rounds in the car the journalist was in, were freaked out, as they are every moment they are in patrol, because a bomb car could explode and blow them up in little pieces in any moment.
I saw a recording of an american patrol in a HUMM-V, they were nervous yelling at every car that came near them and firing warning shots. And that was normal traffic.
One of this days (if it did not happened already) they are going to shoot a car that drives at high speed, confusing it with a bomb car, and they'll end up killing a pregnant women that was on his way to the hospital.
The truth is that you can't really tell when it is a bomb car (they don't have it painted on the sides), and some apparently peaceful diver could rush for a check point, drop a bomb and BUM!
But if the US troops in the area were warned about the rescue operation why did they opened fire on them? Did they confused them? The patrol was not aware about the rescue because they were not properly informed? Did they freaked out and the situation went out of control? Or was there something else?