The bloody fight I mentioned in this post revealed more. The kid who did most of the ass-kicking had a box-cutter on him. I also found out that he kid he beat up was one of mine two years ago. A nice kid, big pot-head, but sweet. He just has the unfortunate ability to piss people off and not know when to shut up sometimes. Hopefully he wasn't so high at the time that he actually learned his lesson.
Maybe this would be a good time to install metal detectors? I've seen enough kids freak out when they see what they think is a metal detector in the library (it detects smuggled books) and refuse to go through it to know that maybe it would be a good idea.
Further Update: A fight in the cafeteria and one of my favorite students balled up his fist and threatened to punch the math teacher I work with. He arrived late to class and the math teacher's abrupt attitude with him set him off. Sigh.