It happened when you "finish them off"... Killing weapon is "player", It's a known bug and I'm fixing it after work today. I even set my name to "NOTE2SELF: FIX RANKS"...
There are a few other issues too...
Also, for future reference, the important line isn't actually the line you selected, it's the one 2 lines down that start with "[N1G-Debug] Weapon [weaponname]"
Thanks for posting the bug though, this kind of stuff makes my life a lot easier
