I was gone for five minutes...
So my very first long-term campaign was me (a LG tiefling cleric) and four other players of dubious allignments. It was always a real struggle keeping us from just being a bunch of horrible horrible people. At the same time, I (irl) was socializing a future guide dog puppy and took him out to pee after saying what my next turn would be in a combat against a band of orcs.
So there I was waiting patiently for this boy to pee (he did), and when I came back, every one of the orc corpses had been stacked into a pile and lit of fire. I turn to my druid friend who’s the closest thing to a good person in the group and go “I just went to use the bathroom, how could you have let this happen!” and he just says “I was a spider at the time.”