(Slip! Slide!) Ahh...made it through the cracks, and here me be without even having to kick, shove, push, bump, pinch, or poke! 
Crazd, 2 things: Noted BC commiserating for your loss, wanted to pitch in, went back a bunch of pages, still didn't find out who's passing? People person? Critter person? Person-in-script person? Hel-l-p! I'm ignorant and it shows!
Item 2: Weapon. Why a gun, knife, or sword? How about a nice chunk of PVC pipe? (Plastic pipe.) It's used for lots of plumbing, sometimes for building things, and it shouldn't be too hard to make it believable that a chunk could be lying around.... Don't know the size of your teacher, but that's another good thing about PVC: Comes in ALL sizes. For ME as the user, I'd go for about a 4 foot piece in 1 1/4" diameter.
But for, say, a 5' 3", 110 pound female with reasonably normal muscles, then maybe either 1" or 3/4" and something like 3 feet in length.
Great "weapon points" for PVC: It's LIGHT, so it can be swung a LOT faster than a baseball bat while needed much less wrist power to get the job done. It FLEXES a little, to the shock to the user on impact is lessened. And yet it's HARD enough that a good lateral swing to the throat would be a killing blow 9 times out of ten, and I wouldn't be one bit afraid to use it to take out a knee--if pursuing the bad guy from behind, a good swing could BREAK a knee if it came in from the side--or knocking him flat out in one shot if a side-blow caught either the temple area or (if the right angle) the base of the skull.
Wouldn't trip any metal detectors, and even if noted by a law enforcement type, could easily be explained away if you think fast on our feet.