Officials with the Vermont attorney general's office said a Brattleboro police officer and two state police troopers who shot and killed a man in July will not face charges.Officials said the officer and troopers were justified in their use of deadly force against Matthew Davis, 34.He was a person of interest in the shooting death of his ex-girlfriend, Mary Anderson, 23, of Harvard, Massachusetts.Anderson was last seen in Hudson, New Hampshire, before she was reported missing.Investigators said Davis ran from law enforcement officers who were trying to question him, then lunged at them with a knife before he was shot and killed.