There are many ways a hospital “gun free zone” can become the scene of a firefight.
In Atlanta several decades ago, when my wife worked in the county hospital as a medical student, a security guard found his wife in the ER waiting room, sitting next to her boyfriend. The security guard started shooting with his legal firearm, and the boyfriend apparently returned fire with his own illegally carried gun.
I don’t recall the outcome of this public display of domestic violence, but do recall my wife adding it to her list of amazing events at the hospital. In later years, the kidnapping/carjacking/murder of a female doctor from a hospital parking deck and gang shootouts in the ER were added to her list.