When police officers searching a home in Calgary, Canada, last month walked inside a backyard shed, they sensed something was amiss.

The floor, Staff Sgt. David Sweeting told reporters Tuesday, felt “kinda spongy.”

Officers removed the wood beneath their feet and found themselves staring at a trap door, one that led to an elaborate underground tunnel that extended eight feet into the earth down a ladder and another 30 feet into the homeowner’s suburban backyard, according to the Calgary Herald.

Packed inside the underground chamber, investigators made an even more shocking discovery: a bounty of stolen property worth $65,000 to $100,000. With enough merchandise to fill a small pawn shop, the items recovered — documented in a police Flickr album with more than 100 photos — included bicycles, tools, purses, clothing, electronics, sporting goods, and five firearms and ammunition, police said.

“One officer (about six feet tall) could stand up in it and you could have two people pass side by side,” Sweeting said, according to the Herald. “In my 36 years (as a police officer), I’ve never seen one.”

Police have charged Douglas Scott Pentland, 50, of Calgary with 15 counts of break and enter and one count of possession of break and enter tools. The massive scope of the thefts has caused police to investigate additional breaking and entering crimes in and around Calgary, police said in a statement posted on Facebook.

“It is believed that the offender targeted residences by forcing entry to basement windows and by prying open overhead garage doors to release the emergency manual release mechanism,” the statement said.

Photos of the tunnel posted by police show a dimly-lit  but intricately constructed chamber reinforced with lumber on the ceiling and walls and strung with Christmas lights. Sweeting told reporters that the tunnel was dug using hand tools and the architects managed to avoid damaging utility lines. After the local fire department was called in to inspect the tunnel’s stability, the chamber was labeled unsafe and destroyed, the Herald reported.

“Any time amateurs dig a tunnel, it is dangerous,” he said. “There were trace amounts of mold in the tunnel, which is dangerous. There’s always the possibility of the tunnel collapsing while they’re digging it. It was definitely not safe to be in.”

Pentland’s neighbor, Val, who did not want her last name published, told the Herald that Pentland had been living at the home for five to 10 years, but she had “no idea” her neighbor “was digging a hole” and suspected he must have done so at night. She and her husband had a good relationship with him, she said, so much so that she allowed him to go into her home and let their dogs out if they were coming home late from work.

“He was a good neighbor,” she said. “I’m not saying anything bad about him. He never did us any harm. He was the kind, gentlest man. Like I said, you think you know your neighbors, but you don’t.”

But  Elvis Gorenko wrote on the police Facebook page that Pentland was more open about his love of digging.

“I rented a room from the suspect at the house for almost 2 years leading up to the raid,” he wrote. “We didn’t talk much but when he started digging the hole, he showed it to me in a boastful manner several times. He said creating tunnels was a hobby he enjoyed for a long time. This was no earlier than September 2015.

“Last time I was down there was following a Football game in early December,” he said. “This was another time he was boasting about the tunnel and I can assure you there were no stolen materials down there at the time.”

The Canadian Broadcasting Corp. reported that some of the stolen items were sold on the classified online advertising service  Kijiji, while others have been returned to their rightful owners.