In the beginning of Greg Rucka's 2011-2012 series (Volume 8, I believe), I never quite understood the background between the wedding massacre that started Rachel Coles' problems. We see a group of men enter the wedding, one gets hit (I think) and gunfire erupts, and we're later told they were the Exchange and it was a gunfight with another gang. Are we ever told who the other gang was (I read online it was the Owl's people), why they were there, where they (the other gang) were, why they picked a wedding to have their high-noon showdown etc etc? I never quite "got" the background to it, even after re-reading the issues a few times.
The Exchange thugs were chasing after one of Owl's thugs, Owl's guy barraged into the wedding and was killed. The Exchange now had a room full of witnesses so they opened fire on the wedding guests. The whole point was to make Cole another victim who lost her family to random mob violence like the Punisher did.