Can you put bear traps in the garbage? Or poison whatever it is they're after in the bins? Motion detector floodlights might be a less violent solution.

And I know how already have more than enough on your plate, but if you can find out what happened to Sarah, perhaps there's a way of saving her if she's trapped? Though you'd have to request a triple room next semester then...

Also, if it helps: my first job I broke all the champagne glasses my first night cause i didn't know you couldn't put them in the dishwasher.