Well, CNN seems to make it pretty clear to me...
The ministry said the incident began around midday, when a convoy of sport utility vehicles came under fire from unidentified gunmen in the square.
The men in the SUVs, described by witnesses as Westerners, returned fire, and the witnesses said the vehicles are that Western security firms use.
A witness told The Associated Press that he heard an explosion before the gunfire began.
"We saw a convoy of SUVs passing in the street nearby," Hussein Abdul-Abbas, owner of a mobile phone store in the area, told the AP. "One minute later, we heard the sound of a bomb explosion followed by gunfire that lasted for 20 minutes between gunmen and the convoy people who were foreigners and dressed in civilian clothes. Everybody in the street started to flee immediately."
www.cnn.com...
Looks like they were ambushed to me, I don't really have an opinion about Blackwater, but if I were attacked, I would shoot back too. Don't blame them at all, what else would anybody expect them to do?
OOO. 
