Authorities are investigating whether a long-running grudge led to the shooting death of an 82-year-old retired lawman.
 
     Eighty-one-year-old Charles Hammer is accused of gunning down Herbert Proffitt last month in his driveway while he was fetching the mail.
 
     The killing rattled the tight-knit town of Tompkinsville, where the victim's only son is mayor.
 
     Residents and law enforcement say Hammer had a history of violence, with multiple arrests on charges of public intoxication, disorderly conduct and more.
 
     Proffitt was formerly the town's police chief and the county sheriff. In 2002, he arrested Hammer on multiple charges. State police say they believe revenge could be a motive.