Currently drugged and laid out in the operating room of Red's clinic, Timebomb was severely wounded during the last super mutant attack, when Red and Shorty were kidnapped. He is known as Timebomb due to his mood swings; he has prolonged periods of calm before instigating big disturbances.
Timebomb, like every other person in Big Town, came from Little Lamplight. If the player speaks to Bittercup, she will say she had a relationship with Timebomb. If you speak to Timebomb about this, he will have no recollection of it, implying she may have "had a relationship" with him while he was unconscious and alluding to Bittercup's fascination with death.