Strong words considering you have no idea whether or not this guy suffered from mental illness. What it does appear is that he killed himself as a result of not wanting to deal with the consequences of his actions. He murdered someone and either didnt want to face the music of life in prison or couldnt deal with his own feeling of guilt over it. Cowardly. This is completely different from someone who kills themselves because they are mentally ill.
So what I hear you saying is that it is normal human behavior for a normal thinking human to take a gun and shoot his girlfriend in the head and then shoot himself??