SOUTH WELLFLEET — Dozens of police, firefighters and dogs spent days searching for a missing man on a remote island surrounded by marsh, but it was a drone that ultimately located the body of William Fleming on New Year’s Eve.

Police started the search for Fleming, 56, on Monday after his 2014 Toyota pickup was found stuck on a dirt road in a secluded area of Lieutenant Island. The low-lying island is inaccessible during extreme high tides and surrounded by hundreds of acres of marshland. Fleming’s family had reported him missing on Dec. 20, according to the Yarmouth police.

The Massachusetts State Police had planned to bring a helicopter to assist with the search for Fleming, a retired Barnstable firefighter. But on Thursday, low clouds and fog grounded the aircraft, said Mashpee firefighter paramedic James Hall.

So, Hall volunteered to use his DJI Phantom drone. Using the remote-controlled flying machine, he searched from about 100 feet above the difficult terrain of scrub and tall marsh grasses, he said.

Hall had to keep switching batteries, which ran out every 20 minutes, and was on one of his last passes right before noon when he saw a color differentiation in a marsh area that caused him to dip the drone down for a closer look, he said.

Hall found Fleming’s body about 30 feet off the island, in an area that was so muddy and wet it wouldn’t be safe to search on foot, said Chatham Fire Capt. Nelson Wirtz, who is a coordinator for the county’s Technical Rescue Team.

Hall had just started his own side business operating the drone for real estate, land surveying and other purposes, he said. As a firefighter, he also thought it would work well for search and rescue situations like this one where the state police helicopters couldn’t fly, he said.

“This is another tool that fire, police and technical teams should be considering,” Hall said.

Once Fleming's truck was found, police from several departments looked for him for two days with traditional methods, bringing in the 35-person Barnstable County Technical Rescue Team on the morning of New Year’s Eve.

Using a grid pattern, the rescue team moved methodically over the island, which is estimated to be 60 to 70 acres and contains 111 private homes, according to Terri Gerber, treasurer of the Lieutenant Island Service Improvement Company, a homeowners association.

Though he operates the drone as a business, Hall had no intention of charging for this mission.

“This is for a family that needed someone to come home,” Hall said. “Firefighting is a brotherhood, and he was one of our own.”

Fleming's family members were touched by the effort of as many as 50 police and firefighters who turned out to assist in the search, said Stephen Tebo, Fleming’s nephew.

“Everyone was just wonderful, they were so accommodating,” Tebo said.

Tebo described his uncle as “a true firefighter through and through.”

“He would do anything for anyone,” Tebo said.

Fleming grew up in Hyde Park and moved to the Cape after his parents relocated here, Tebo said.

He joined the Barnstable Fire Department in 1990 and retired in 2009. He leaves a son and a daughter.

“No matter where he and I went together in whatever state, he would know someone through firefighting,” Tebo said. “He was very outgoing.”

Tebo said the family especially wanted to thank the Barnstable Fire Department, the Barnstable County Technical Rescue Team and the Wellfleet fire and police departments.

“They were so professional ... Billy would have loved to see what they had done for him,” Tebo said.

Tara Miltmore, spokeswoman for the Cape and Islands District Attorney's Office, had no comment Friday on the investigation into Fleming's death.

— Follow K.C. Myers on Twitter: @kcmyerscct.