Jack was a younger, Ex-Navy Seal. His body was lean, but still no where near where it could be. Yet, the training and the knowledge that he gained in that time rarely seem to show due to a combination of PTSD and Depression that formed itself into a war-torn hero into a mental patient. He had developed DID, a multiple personality disorder that his brain used to try to escape him pain. If the brain cannot handle a certain amount of stress, it may make an entirely new life with a complete new set of memories and personality type. They can no longer recall their past life and won't until they are forced to via certain types of therapy, through minor panic attacks, and when the brain feels it can handle the stress. The only current recorded personality is "Jack", but he has mentioned many more are there.