Bobcat, hope you 're feeling better. It seems like you have identified many of the problem areas.. i.e. being expected to care for a potentially dangerous patient, alone, in a closed room, with an ineffective surveillance system. As there is a protocol, one presumes that the behaviour is not new, and this combined with the other aspects of your description of the event would suggest that your employer is not providing a safe workplace, or safe systems of work.
I would explore your case with a lawyer, and perhaps talk to OSHA if not a union rep. Meanwhile, make sure the incident is recorded, and don't enter that room alone, certainly not with the door closed.