UPDATE:  A couple charged in the December 2015 death of a man at the Chickamauga and Chattanooga National Battlefield pleaded guilty to charges Monday.

Fifty-nine-year-old Duane Hollenbeck's body was found on a trail at the popular national park

Robert Martin Brooks was charged with voluntary manslaughter and was sentenced to 20 years. Jennifer Allison DeMott was charged with aggravated assault, and was sentenced to 10 years with a 10-year probation.

PREVIOUS STORY: Two suspects have been arrested in the death of Duane Hollenbeck, a New York man whose body was found at the Chickamauga Battlefield on December 12, 2015.

Jennifer Demott, of Geneva, NY, was arrested and is in the Catoosa County Jail.

Robert Brooks, also from Geneva, NY, was arrested a few days later. Brooks is currently in Knox County Jail and awaiting extradition to Catoosa County. 

Both have been charged with felony murder.

"What our investigation revealed was that Ms. DeMott and Mr. Hollenbeck knew each other," said Park Ranger Chief Todd Roeder, "They asked Mr. Hollenbeck to go on a road trip to the North Georgia area, Tennessee area."

Somewhere along the trip, police say DeMott killed Hollenbeck by striking him in the head with a blunt object. But details like when, where and why Hollenbeck was murdered are still unknown.

"That's a good question, I'm still trying to find that out, I don't know that," Chief Roeder said.

By the time police had enough evidence to make the arrests --- both DeMott and Brooks had left Georgia.

'It's my understanding that she was located back up in New York, they went back up to New York."
Brooks was arrested in Knoxville, Tennessee. He is now awaiting extradiction to the Catoosa County Jail.

On December 12, 2015, visitors at the National Park reported a body near a trail in Chickamauga Battlefield.  

Park rangers began their investigation and Hollenbeck's body was transported to Atlanta for an autopsy, which has not yet been released, while waiting for the toxicology report.

Detectives on this case learn that Hollenbeck suffered blunt force trauma to the head, according to the GBI. DeMott was also charged with exploitation of an elder or disabled person as part of murder investigation. Police say Hollenbeck was physically disabled and needed a cane or a walker to move around.

Multiple agencies were involved in the case: Fort Oglethorpe Police Department, Georgia Bureau of Investigation, Federal Bureau of Investigation, Catoosa County Coroner’s Office, New York State Police and the National Park Service. The case is still ongoing.

PREVIOUS STORY: National Park Service Chief, Todd Roeder tells Channel 3 the man found dead in the park is Duane L. Hollenbeck, 59.

Two hikers found the man's body right off of a popular trail at the Chickamauga Battlefield. The Chief Park Ranger says they believe the man was dead for less than 24 hours before his body was found

"It was along the path, it's called the red trail, it was our horse equestrian trail around the park," Chief Roeder said, "It's about a seven-mile loop around the battlefield here."

No evidence of a horse was found near the body, no identification was found at the scene, and no car was found on park grounds.
Chief Roeder says there are still a lot of questions the FBI is hoping to help answer.

"When we found him he was lying in the creek bed and he did have a laceration to his forehead," Chief Roeder said.

The man has been identified as 59-year-old Duane Hollenbeck.
He was reported missing from his home in Dryden, New York by a neighbor on December 8th.
Hikers found his body more than 850 miles away at the Chickamauga Battlefield four days later.

"We're trying to figure out how he got here and what purpose he was here in the park for," Chief Roeder said, "Was it strictly hiking? Was he visiting because of the Civil War? We don't know."

Some of Hollenbeck's family members didn't find out of his death until Monday morning and they are still processing their loss.
His niece says Hollenbeck was a "kind, caring, loving man who would give the shirt off his back for anyone."
It's still not clear why or how Hollenbeck went missing. Chief Roeder says he is not aware of any connections Hollenbeck might have to the area.

"I can't determine that right now if it was an accident or a homicide," Roeder said, "We're keeping the door open until GBI gives us a report on that and finds out what the cause of death was."

The FBI is assisting the investigation because this National Park is on federal property.

The GBI is handling the autopsy, and expect to have those results within the next few days.

PREVIOUS STORY: The FBI and National Park Service are investigating the death of a man after hikers found his body Saturday.

Hikers called 911 shortly after 12:30pm Saturday to report their discovery of the man’s body off Alexander Bridge Road in Chickamauga Battlefield.

The 59-year-old man from New York had been reported missing on December 8 by a neighbor.

According to Chief Todd Roeder, with the park service, the man had a cut to his head and had likely been dead for less than 24 hours when he was found.

Roeder says it’s too soon to tell how the man died. His body was sent to the GBI crime lab in Atlanta for an autopsy.

The man’s name will be released later today.

Stay with Channel 3 for more on this developing story.