All I was saying before was that gunners like this are used to facing insurgent tactics. When they see vans like this, they aren't looking to give them the benefit of the doubt. They have been trained that, if they do, they may be putting their lives and the mission at risk. This guy is probably scared out of his mind. He has a huge responsibility, and screwing up - as we've seen today - has enormous consequences.
To me, the laughing and joking isn't making light of slaughtering the enemy, it's nervous laughs and desperate attempts to bring everyone out of it. We're human, we don't deal with this shit well. The comments here are good proof of that.
None of this excuses slaughtering innocent unarmed civilians, it's just my attempt at bringing some perspective.
Not that it makes the situation any more right, but it does make things a lot less clear cut...
Also, the original group of Iraqis didn't notice the chopper at all, even though it was circling for a while. They surely would have had a potshot at it had they seen it, as they were supposedly all armed with AKs and RPGs. It's probably quite a distance from the target, with the camera zoomed in creating the illusion its a lot closer than it would appear. Notice the amount of time it takes for the rounds to strike the target. That's why I reckon the van pulled up, he thought the street was empty.