Killer's father has told how his son was struggling with PTSD and says scandal-plagued Veterans Affairs department let him down.Routh will go on trial in February shortly after full release of American Sniper, the movie tipped for Oscars which tells story of Kyle's life.Ex-Marine Eddie Ray Routh shot and killed Chris Kyle and Chad Littlefield at a shooting range where they were trying to help him tackle his PTSD.EXCLUSIVE: 'He'd rather take the death penalty than sit behind those bars forever.' Father of veteran who killed American Sniper Chris Kyle tells how he is already mourning the loss of his own son