What happened to May to cause her to behave the she does ?

As she grew older, May's empathy grew to encompass the struggles and pain of the world at large. May found great sadness in the pain of others. When an unpleasant or sad topic would be brought up in a room, she would hum, "Oh Susannah" and leave. She built a wailing wall as a catharsis for her pain, but she remained unable to bear the weight of the world. She ultimately took her own life as well.