Or you we can just take to shooting thugs in masks, like Ben mentioned.
I'm OK with this.
Yup. I think pretty much every firearms self-defense class I've taken, and probably what most teach (with many having LE as teachers), consider what happened to Ngo a clear, "shoot until they're no longer a threat" situation. Obviously you have to deal with the legal implications, especially with say, the Potland, OR prosecutor's office, but this kind of crap is getting out of hand. All it would have taken is a punch to another part of Ngo's head, and he might very well be dead right now.
These are basically rabid animals, and they need to be dealt with accordingly.