When dealing with people who are unstable and threatening, there's only one way. Record, record, record!
Most people have never had to deal with someone who is severely unstable, and find it hard to believe such behavior could be possible. That's why you have to have objective records of the behavior.
It's not illegal to make recordings of situations in which you feel threatened. Especially if there has been a repeated pattern of threats and abuse.
Small audio recorders are cheap, and can run for days. Get one that records to plain WAV files, since that's non-lossy. A/V recorders are a bit more expensive, and also have the downside of having to deal with very large data files. Which since in these kinds of situations you need to record almost full time in order to catch the 'peak-freaky' behavior, can be a burden.
I've been through something similar. Even if you don't end up giving the the recordings to police/authorities, having them is immensely helpful in a personal sense, since you can review them in future and reassure yourself that yes, it really was the other person being batshit insane. It's a horrible feeling if you start to wonder whether maybe you were somehow to blame. As memory of details fades, you may start to doubt your own viewpoint.
Plus, there's always the chance the the nutter will actually become physically violent, and you'll have to defend yourself in some way. After which, recordings of them being a lunatic are extremely valuable. (Yes, in my experience.)
And lastly, don't let yourself be victimized and disadvantaged by such arseholes. Stomp on them as fast as you can, then get on with your life and work. Why should you have to move to another lab if you don't want to? Play recordings of the person abusing you, to your superiors. The end (for him.)
Every time you turn the recorder on, remember to announce the date and time immediately. This helps a lot when dealing with backlogs of recorded files. Retain this in the file, and do not make cuts between this and evidence. You can cut long silences off the *end* of recordings only.
Name files with date prefix in the form YYYYMMDD, so they always sort in time sequence.
Don't carry it in your pocket unless absolutely unavoidable. Clothing noise can obscure the fainter sounds of interest. Put it on a shelf or somewhere else in the room that won't get vibrated or knocked.
Oh and the worst part? In organizing and cutting down the files, you'll have to listen to yourself a lot. Can be painful. But it does help teach 'engage brain before opening mouth'.