I've been trying to clear out the Saints Book, and I was working on Angel's "No-Weapon Kill" challenge.

I assumed this was simple, and I'd go up to cops/gangs and punch the crap out of them for a bit and get it. But, as this album attests to, I beat up the cops for a while. When I checked my progress on the challenge, though, I was still at 14/25 kills.
Clearly, at some point through playing the game, I've gotten 14 kills the game considers "no-weapon" kills, but I have no idea what I would have done to get them to count. I would have thought at least the wrestling moves would count, since that's what Angel would have wanted, but I made absolutely no progress towards the challenge.
What the heck does the game mean by a "no-weapon kill?"
