The manager of a part-time census taker who died under mysterious circumstances in southeastern Kentucky says other workers are requesting to visit houses in teams rather than alone.

Wayne Hatcher, regional director of the U.S. Census Bureau's office in Charlotte, N.C., made the comments Sunday at a memorial in the Daniel Boone National Forest near the spot Bill Sparkman's body was found one month ago with the word "Fed" scrawled on his chest, likely in pen.

Sparkman was tied to a tree with a rope around his neck.

An autopsy concluded Sparkman died of asphyxiation. However, authorities are saying little else about his death, even whether it was a murder, suicide or accident.

Hatcher says door-to-door visits in Clay County are suspended until more information is known.

Sparkman, 51, was a substitute teacher and part-time census worker.

Josh Sparkman, 19, said he learned of his father's death Sept. 13, a day after his body was found. Sparkman adopted him when he was a baby.

He believes his father was murdered.

Josh Sparkman told The Associated Press in a phone interview that he was frustrated investigators have not ruled out suicide or accidental death.

"I look at it as disrespectful to be still throwing suicide and accident around," he said. "He didn't do this to himself. That's dishonorable. My dad was a good man. No person on this planet is going to fight cancer like he did, then turn around and kill himself a year or so later."

The Associted Press contributed to this report.