I'm going to call the police just to be on the safe side.
Do you feel like you are in immediate danger?
This is not a threat in the traditional sense, this action is a preemptive measure in order to prevent it.
If you feel like you are in danger you should take steps to protect yourself. It might also help removing yourself from a bad situation if you can before trouble happens.
I might have to actually call 911 and hope they take this seriously.
You do what you need to do to protect yourself. You need to make sure you are safe.