KNOXVILLE, Tenn. (WATE) — One of East Tennessee’s oldest missing persons cases has a more shocking story than that of a simple outdoorsman who went missing near the Great Smoky Mountains National Park, FBI reports reveal.

William Bradford Bishop, Jr. was last seen alive on March 2, 1976, at a sporting goods store in Jacksonville, North Carolina according to the National Missing and Unidentified Persons System (NamUs) website. His car was found at Elkmont in the Great Smoky Mountains National Park just over two weeks later, the profile says.

At the time he went missing, he was 39 years old, and sources say in addition to being an outdoorsman, Bishop had an American Studies Degree from Yale University as well as a Master’s Degree in Italian from Middlebury College in Vermont. But an interesting note stands out on the NamUs profile,

“If located, do not approach or contact Bishop. Notify law enforcement immediately,” the note reads.

According to the FBI, just one day before he was last seen, Bishop allegedly bludgeoned his wife, 37, mother, 68, and three sons, 5, 10 and 14, to death in Bethesda, Maryland. The former U.S. State Department employee found out that day that he had been passed over for a promotion, the FBI says. According to the FBI, Bishop was described as “highly intelligent” as well as “intense and self-absorbed, prone to violent outbursts, and preferred a neat and orderly environment.”

“To be able to take a hammer to your children’s heads and faces while they’re sleeping think really exhibits the brutality of the crime,” case agent Charles Adams said in an FBI video.

In a video on the FBI’s website, case agent Charles Adams said Bishop drove his family’s bodies to North Carolina where he dug a shallow grave and then set them on fire. When he was seen the next day, the FBI said Bishop was buying tennis shoes with a woman his age and what may have been the family dog.

In March 1976, the FBI says Bishop was charged with murder by the Montgomery County Sheriff’s Office in Rockville, Maryland, and federally with unlawful flight to avoid prosecution.

After nearly four decades, Bishop was added to the FBI’s Most Wanted list on April 10, 2014, as the result of Special Agent Steve Vogt’s work to form a task force and renew efforts to locate Bishop through a publicity campaign. A $100,000 reward was offered for information leading to his arrest.

In 2014, the FBI believed Bishop might have assumed a new identity and was hiding in plain sight in the United States. If he were found today, he would be 86 years old. The TBI adds that he was a licensed amateur pilot who learned to fly in Botswana, Africa, and that he had an “aptitude” for learning languages. According to the report, he speaks English, French, Italian, Serbo-Croatian, and Spanish.

Bishop was, and could still be, an experienced outdoorsman, camper, and hiker, the FBI says. According to his profile on the FBI’s website, Bishop enjoyed canoeing, fishing, swimming, jogging, tennis, skiing, and riding motorcycles. He was also known to read extensively and could have kept a journal, it says.

In 1976, Bishop was 6’1″, 180 pounds, with brown hair. Notably, the FBI says he had a six-inch vertical surgical scare on his lower back.

The FBI says anyone with information about Bishop and where he might be should contact the nearest FBI office or American Embassy or Consulate. According to NamUs, the case was investigated by the Montgomery County Department of Police in Gaithersburg, Maryland.

Editor’s Note: This story has been updated.