That's not necessarily the case. Being gunned down is distinctly different than being killed in a firefight. One of these men was killed in a drive by shooting. That's not a firefight. That's being gunned down, regardless of whether or not you had it coming.
That would be true if you take the word of regional police, who may themselves be either Sunni or Shi-ite and thus have an agenda. Notice that US authorities are NOT cited. That makes this one-sided and likely propaganda for the other side.
I'm not buying this until the whole story comes out, if ever. I think these men were killed in war and that the story is slanted to date against my country. Hence, I am at best skeptical, especially given the reporting outlet, not to mention the 'sources'.