Or could it be they want to plan ahead on how to kill/eliminate physicians who would be working to save the injured in a large scale attack? They were visiting emergency room areas....why weren't these people arrested?
Most hospitals now have cameras which observe the hallways. Hoping they are working to find out who these folks are, exactly where they went, and then ARREST them for trespassing at the least.
Any one wandering around a hospital would be questioned by security...much more should have been done in this case than simply asking them to leave. There is a pattern here. This is occurring in other hospitals....
Eventually....after someone notices them!