"But he was so normal ..."

When someone goes on a shooting rampage, guess what becomes the defining action of his or her character?
Was it the fact that he or she brought flowers to little old Mrs. Hickendoopler down the street, once, when he or she was 11 years old?
No.
We are defined by our actions, and certain actions carry larger stigmas. For example, shooting a crapload of people across two counties in Alabama. Or being Chester the Molester.
Sorry, maybe I'm going to Hell for saying this, but Ned Flanders he is not.
So why do people feel the need to insist that this person who shot all these people "was so normal. He was so quiet."
He's not normal. He cannot function as a healthy individual in society.
But for those people who want to make excuses for him, invite him over for tea. See how that works for you.