Just happened to me:

I managed to put some paralising poison then ordinary poison on this guys pocket.

After diying, he doesn't 'bailed out' like everyone else. His corpse started to move back and forth.

I LoL'ed hard on this. I tryed to repeat the feat and succeded. Just put the paralising poison first.

Some SS's:
http://steamcommunity.com/id/bruno7317/screenshot/631859135383466753
http://steamcommunity.com/id/bruno7317/screenshot/631859135383471340