Henry Bello, 45 — who resigned amid a sexual-harassment scandal — fatally shot a physician and wounded six other people with an assault rifle before killing himself, officials said. “When he left he promised to come back and shoot one of the residents,” Dr. Maureen Kwankam told The Post about Bello.“He said the resident will never graduate and become a doctor because he will kill him before he has the opportunity.”Before he was canned, the deranged doc had threatened to harm at least four other people working at the hospital, Kwankam said.He also called the resident once on the phone...