KNOXVILLE, Tenn. — It has been a year since a Maryland man vanished while swimming in Tellico Lake. 17 days after the search for Michael Carnock began, crews found his body. 

The Loudon County Sheriff’s Office said Wednesday that there are still few answers about how he died and who may have killed him. 

The sheriff’s office is actively searching for leads about who may have struck Carnock when he was swimming. Carnock’s family posted billboards around Loudon County in an attempt to learn more information. 

The case is still open, with more questions than answers. 

"It was extremely challenging. A lot of organizations involved. 17 days searching from dusk until dawn," said Rick Papke, the Deputy Chief of the Tellico Village Volunteer Fire Department. "It looked like a propeller had run over him."

RELATED: Active search ends for missing Maryland man in Tellico Lake

Loudon, Tenn. - Update: Wednesday, May 23 The active search and recovery effort has ended for a Maryland man who went for a swim more than a week ago in Tellico Lake and never returned. 55-year-old Michael Carnock Sr.

This time last year, Rick Papke and the Tellico Village Volunteer Fire Department began a more than two-week search for a missing swimmer. 

It took helicopters, a drone, and even sonar equipment to locate the experienced swimmer. But the search didn’t provide many answers about why he died or who may have killed him.

Rescuers said it is often hard for boats to spot swimmers in the water. 

"You’re looking around the lake, you don’t see what’s in front of you. Even if you feel a bump, a lot of times you run over a piece of floating log, people don’t pay much attention to that," said Papke. "We have a lot of boats on the lake and some of them are traveling pretty fast, 50 or 60 mph. We have some big cruisers where people are up on a tower and they can’t see what’s in front of them, especially a small swimmer."

Papke warned boaters to be wary of swimmers and swimmers to stay out of the middle of the lake. 

"If you’re taking your boat out, beware of what’s in the water. There are a lot of people who could be swimming out there," said Papke. "If they’re going to swim out in the main channel, they really need to have another boat with them to protect them or at least have an attachable rod with an orange flag on it showing that there is, in fact, a person in the water."