Run For Your Lives!
The party shows perhaps a bit too much compassion, and as a result ends up fighting another bunch of goblins. Metrius, the simple Paladin who wants to rescue the innocent goblins in the Deadmines from, uh, themselves, strides forwards at the beginning of combat to warn them that they are in danger and must flee!
It's true, as the rest of the party start attacking these goblins. It doesn't matter that the goblins started attacking at pretty much the same time, if not before, as the adventurers. Nevertheless, Metrius urges the goblins to flee. As he does so, the foreman of the goblin workers decides to take this advice, after a barrage of fire from the party viciously wounds him.
As he turns to flee, his defences naturally drop. The party member standing next to him sees an opening, and strikes with an attack of opportunity! His sharp blade catches the turned goblin right between the shoulder blades, landing a crushing and mortal blow, and the now-splintered goblin collapses in a bloody heap on the ground.
The death-bringer would probably have got quite the rebuke from Metrius, who wanted to save all the goblins, if it hadn't been Metrius himself who struck the escaping goblin. Instead, a meek 'oops' was all he had to say.