I worked in a hospital for about 4 years. Everyone in the building is trained to see and respond to triggers of agitation that lead to a violent outburst, outbursts are standard day to day fair at a hospital. People don't always like what they hear when it is not good news and there are all sorts of behaviors that kick up when people jump from denial to anger. In my experience a loud person is not really a threat, they are acting out to get attention or are huring and need help. In my opinion you were in a yellow level threat situation worth paying attention to, but it would not have raised my heart rate much to be honest, seen it 100 times. Maybe just scan and know where all the exits are and sit closer to them. I'm unaware of any incidents taking place in hospital waiting rooms, maybe there have been, but I don't think it is a high risk place to be unless you live in Ukraine or Israel.