This particular jihadi recepticle was stationed under the kitchen sink (nominally) providing logistics support for a dish washer and garbage disposal. Typically a unit of this sort would be wired up with a "split feed" (as this one was), which means the recepticle has 240V coming into it rather than the more common 120V. The top half of the plug gets 1/2 of the 240V, the bottom half gets the other half, but there is 240V on the cable feeding the offending device. [I'm vastly simplifying this lashup for non-electricians].
In this case, the "root causes" of this quashed rebellion were sown back in 1989 when the house in question was built. That's right -- it was preordained to occur even before the house had its first occupants.
An astute researcher would find that a while ago UL stopped listing recepticles for backstab using 12 gage wire, because they were tending to do as this one did trying to start fires. Naturally, there was no nationwide public information campaign launched to inform the public that there were millions of these frigging terrorist recepticles "in the field" that would inevitably fail and try to kill people. No...must not alarm the public.
However, UL in its infinite wisdom decided to keep allowing the evil backstab scheme for the smaller 14 gage wire (found on 15 amp circuits). These too will fail over time. The only advantage of this scheme is to the installing electrician -- THERE ARE NO ADVANTAGES FOR THE CONSUMER. It allws the installation to be a tad faster than the time tested "wrap the wire around the screw" technique.