Four decades after beating his mother, wife, and sons to death with a sledgehammer at his home in Bethesda, Md., federal and local officials have added former State Department foreign-service officer Bradford Bishop to the FBI’s Ten Most Wanted Fugitives list. Bishop, who is fluent in five languages, would be 77 now, and officials believe he is still alive. Forty years ago, Bishop put all the bodies into the family’s station wagon, and set it on fire in a shallow grave in a swamp 275 miles away. Then he disappeared. Officials produced an “age-progressed” sculpture to show what they think Bishop’s face may look like today, and hope that the reach of the Web and social media will help them in their decades-long search.