I think it was Gimli who killed him in anger when he thought the orc killed Frodo (in the movie version).
To misquote Barbie, Weight painting is tough! (and I’m a mathematician so I…well, I do think math class is tough once you get to the graduate level anyway!!!) What worked well on Orc Idle (but still with the arms intersecting the torso; orc is thicker than the human rig the animations are made for) gets glitchy when the orc dies.