Drone Spotted T-Shirt Believed to Be Travis Decker's in 'Very Rugged' Terrain Less Than a Mile from Where Daughters' Bodies Were Found By Christine Pelisek

A drone spotted a T-shirt that led Washington state authorities to human remains believed to be those of Travis Decker.

Chelan County Sheriff Mike Morrison tells PEOPLE that on Thursday, Sept. 18, the drone spotted an “anomaly” around 3 p.m. “They shared the image with me because it was a live feed and I saw it and I was like, that’s a pretty good clue,” he says, noting that the neon green shirt had matched the same kind of shirt they had seen Decker wear before.

“You couldn’t just see it temporarily flying over,” Morrison says. “You had to get very much down on the ground. It was more embedded into stuff blended in.”

Due to the “very rugged” terrain, he says, officers were repelled down to the location by a Spokane County Sheriff’s Office helicopter.

Once there, they discovered the remains which were “well decomposed,” according to Morrison.

The Chelan County Sheriff’s Office announced later that evening that they found human remains they believed to be Decker’s in a wooded area south of Leavenworth, Wash.

Authorities had been searching for Decker for more than three months after the bodies of his three daughters — Paityn, 9, Evelyn, 8, and Olivia, 5 — were discovered in a remote area of the Rock Island Campground in Chelan County, Wash., on June 2.

Decker, 32, had failed to return his daughters to his ex-wife, Whitney Decker, in Wenatchee, Wash., after taking them for a court-ordered visit on May 30.

At the scene, authorities also found a pair of shorts and a bracelet.

“Clothing is consistent with what we’ve seen in surveillance. Also, additional personal items that we have photos of him wearing in the past,” Morrison says. “His shorts and his shirt match images that we’ve seen him wearing before too. So, unless there’s someone that just happens to have a similar bracelet and clothing and is in the same general area where we’ve been searching … But until you get confirmation you can’t say.”

Morrison says it was their last day of searching that area when the remains were found.

“We’ve been searching since Monday,” he says, adding that Thursday was their final day. “We were just wrapping up operations. We talked about [how] we just need that one day for things to go our way and we’re hoping [Thursday] was that day for us.”

“To hike that 0.74 miles from where the original crime scene was at to get to the location where we found the remains would take about three hours,” he says. “Three hours to get to the location. Very steep. It was not a trail, it was not anywhere that’s recreated. It’s not anywhere that people typically go. It was in the middle of our wilderness area in a very steep, rocky wooded terrain. Heavily brushed.”

The campsite where Decker’s daughters were found was at an elevation of around 2,800 feet and the remains were above 4,000 feet just less than a mile away, he says.

Morrison says they are still searching for more remains, adding that it’s “not irregular” for animals to get ahold of them and potentially “spread them out over a long distance.”

The months-long manhunt for Decker, which included searches in the Blewett Pass area in the Wenatchee Mountains, spanned across the country as warrants were issued for his arrest. Throughout the search efforts, there were multiple possible sightings of Decker in Idaho and Washington state.

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Authorities had said they weren’t sure if he was alive or dead.

At one point, they suggested that Decker may have attempted to cross into Canada because he allegedly searched “how to relocate to Canada” online, according to a U.S. Marshals Service affidavit obtained by PEOPLE.

The newly discovered remains are now pending DNA confirmation, with Morrison noting that he has requested for the results to be expedited.

“If this is him, he never made it to Canada,” says Morrison.