According to an article in the British Sunday newspaper the Observer's magazine supplement, the fact that he fought in the Gulf War killing at least two Iraqui snipers changed him. His home life was also disturbed. Incidentally it is not the murderer who suffers, it's the victims, their relatives and the relatives of the killers who have to live with the consequences of the actions which result. When McVeigh is dust, his sister and parents still have to try and survive.