Mr. McKay was a construction worker. He took his son to work with him every Saturday, even though his son just wanted to play with his friends instead. He tried to instill a strong work ethic in his son, but ended up driving his wife farther away as he spent so much time away from home.
When his wife cheated on him and Grant discovered it, he was informed by Grant of what happened. He took the actions personally and eventually committed suicide out of disgrace.