The 5-16 investigation and the pictures enclosed in it give the most complete picture, providing context you can't see in the video.
First, the ground unit had declared TIC and the Apaches were on station to support them. The guy peering around the corner was actually one of the journalists taking pictures of a HMMWV just 100 meters down the alley. Given the TIC, his actions, and the close proximity to the TIC unit, you can see why the pilots were spring loaded to attack. They felt they were defending the ground unit that was already taking fire.

I won't get into the engagement of the van, but would be interested to hear from people who actually know the legal aspect as to whether that was a bad shoot or not.