Authorities have not yet said what caused the death of a missing man found dead in a swamp in the Town of Forrestburgh last week.

Rescuers had tried to find him for days. It's a mystery Harold Hoyt's sister is desperate to solve.  

"It doesn't make sense how one goes in, and one never comes out," said Jennifer Nicholas.

Nicholas says her brother's friend told authorities he suffered a medical emergency after their car broke down when they got separated. 

MORE: Police: Missing Sullivan County man found dead in Forestburgh marsh

"Their tire was flat, and they had no gas," said Nicholas. "He got sick and had a seizure. My brother left and told his friend, 'I'm going to get you help.'"

The father of two is from Port Jervis but was living in Glen Spey when he was last seen alive by his friend, who has not been named by authorities.

Officials say his friend reported him missing on March 31.

Their car broke down on a logging trail off Galligan Road near the Camp Turrell Boy Scout Reservation, according to the Sullivan County Sheriff's Office.

Officials say Hoyt's friend made it to a nearby road, but that Hoyt apparently became lost in the woods.

"They began a search party immediately. We searched for him from sunup to sundown every day," said Nicholas.

The father of two was found deceased after an exhaustive search seven days later, on April 7, in a wooded swamp.

"I can't even begin to describe what we feel right now," said Nicholas. "It's devastation. The whole thing has just been a nightmare."

Authorities are still investigating the tragedy, and an autopsy was performed Monday to find out how Hoyt died.

"My brother knew his way around the woods. He knew survival skills. It just makes no sense to me," said Nicholas.

Wake services for Harold Hoyt will be held at the Gray-Parker Funeral Home in Port Jervis from 4-7 p.m. Thursday.