Grim twist in search for missing Wisconsin brothers as sheriff says human remains found on Missouri farm Brothers Nick and Justin Diemel have been missing since July 21.

A mystery of what happened to two Wisconsin brothers who vanished nearly two weeks ago took a grave turn when authorities said human remains were discovered on a Missouri farm where the siblings had gone to do business.

The search for Nicholas Diemel, 35, and his 24-year-old brother, Justin Diemel, who own a livestock company in Bonduel, Wisconsin, has now become a "death investigation," and authorities say one suspect is in custody -- the owner the rural Missouri farm the brothers visited to complete a deal over cattle on the day they disappeared.

"It doesn’t really seem real," Rob Chupp, a close friend of Nicholas Diemel, told ABC affiliate station KMBC-TV in Kansas City. "I can’t understand it. Just trying to figure out why and it doesn’t make sense."

Chupp described Nicholas and Justin Diemel as "some of the best people I've ever met."

The Diemel brothers were reported missing after they failed to catch a flight home from Missouri on July 21, officials said.

Clinton County Sheriff Larry Fish said the search for the Diemel brothers is now a "death investigation," but declined to say why detectives suspect the brothers are no longer alive.

During a news conference on Wednesday night, Fish said human remains were located on a farm in Braymer, Missouri, where the Diemel brothers had gone to purchase cattle.

"A cause of death has not been determined," Fish said. "This is still an active investigation and the human remains have not been identified at this time."

Fish declined to say what condition the human remains were in, or if they were from one or two people.

The sheriff said the Diemel brothers went to the farm in Braymer, about 70 miles northeast of Kansas City, for a business deal to purchase cattle. He said the brothers had been negotiating the deal for a few months.

Nicholas Diemel, a married father of four, and his younger brother were reported missing after they failed to catch a flight home from Kansas City, Fish said. The brothers' rental truck was found abandoned in a commuter lot in Holt, Missouri, more than 30 miles from the Braymer farm.

Fish said Wednesday that one suspect in the disappearance of the brothers remains in jail. Garland "Joey" Nelson, 25, was arrested on Friday after telling investigators he drove the brothers' rental truck to a commuter lot in Holt, where he abandoned the vehicle, the sheriff said.

Nelson is being held in jail without bail on suspicion of tampering with evidence.

Security cameras at a hotel where the brothers were staying showed them checking out of their room on the morning of July 21, and investigators said the GPS on their rental truck showed they arrived at Nelson's farm in Braymer at 9:30 a.m. on the same day.

Authorities said the truck, according to its GPS tracking, left the farm at 11:44 a.m. on July 21, and was captured on surveillance cameras 34 minutes later outside a general store in Braymer. Investigators analyzing the footage saw only the driver in the truck, officials said. Police did not identify who it was they saw on the surveillance video.

The GPS showed the truck arrived at the commuter lot in Holt at 12:45 p.m. on July 21, officials said.

"We have a lot of leads that have come in," Fish said on Wednesday. "A lot of people have provided a lot of support. And we are diligently working on those leads. It’s going to be long-term. It’s going to take some time."