Suffolk County Sheriff’s Office via ReutersFormer classmates say the accused serial killer charged in the deaths of three women associated with the Gilgo Beach murders was an isolated teenager who was picked on in school—and was known for lashing out at those who targeted him.Rex Heuermann, 59, was arrested on July 13 and has since pleaded not guilty to the charges against him. Authorities say he is considered the prime suspect in the death of a fourth woman, with investigators still seeking ans