Emma,
I know the answer to this one because of a college class I took so I will refrain from giving the answer (not an easy one, guys). However, I will share the answer I came up with in the class which got me an A for effort.
The man left the water running when he went back to bed. When he woke he realized the water had caused the bathroom ceiling to fall into the shower below, killing his wife. When he looked out the window, he saw the life squad, who had brought his wife outside onto the front lawn to try and revive her but were unable to do so. He was so despondent (sp?) that he screamed and killed himself.