Martin Springer

Serial killer!

He's a trucker.

He's an ex cop... His wife and three kids were killed in a car crash. His guilt made have have a psychotic snap and a cop co-worker manipulated him into going into the psych ward. He was abused by the doctors there in horrific ways. A doctor took pity on him and broke him out of the ward. He changed his identity and became a truck driver. He picks up victims in his truck and kills them along the way, dumping the bodies anywhere on the highways on mainland BC, Canada. He's known as the West Coast Strangler after the way he kills his victims.

He remains friends with the doctor who broke him free, the doctor helps him clean up bodies sometimes and Martin lends himself as a test subject for his experiments. He receives injections of a super regeneration serum that makes him incredibly difficult to injure and kill. 

He made the detective going after him fall in love with him, convincing the man to explore the dark side of murder.