"This is a long-term investigation," Clinton County Sheriff Larry Fish said Monday about the ongoing investigation into the disappearance of Wisconsin brothers Nick and Justin Diemel. Late last week, the investigation shifted to a death investigation, though authorities have not stated why.

For days, authorities have been searching a 74-acre farm in the Braymer area, where GPS on a rental truck last places the missing men. On Monday morning a Braymer man, Gerald "Joey" Nelson made his first appearance before a judge for charges he allegedly tampered with the Ford F250, which was rented to Nick and Jason Diemel, brothers who have been missing for more than a week now.

Law enforcement used GPS information from the truck’s black box system to match the vehicle on several security cameras.

Cameras at the hotel where the brothers last stayed showed the men signing out of their hotel room on July 21, the GPS then tracked the truck from the hotel to Nelson’s farm, where they arrived just before 9:30 a.m. July 21.

A family member states they spoke with the brothers at 11 a.m., July 21, everything was fine, and they were on schedule to make their 1:50 p.m., flight from Kansas City International Airport back home. Neither of the brothers have been heard from since.

At 11:44 a.m., the truck left the farm again, and at 12:18 p.m., it was seen on a Casey’s General Store security camera traveling south of Highway 13. GPS matched with security camera time codes showed the truck turning south in front of a bank while cameras showed there appeared to be no passenger in the front seat of the truck – only the driver. the truck was also seen on business security footage driving by with only one occupant, and then as 12:45 p.m., GPS shows the truck pulled into a commuter parking lot in Holt off Interstate 35. The truck was left running with the keys in the ignition and the lights on.

Nelson reportedly admitted to driving the truck from his residence to the commuter lot in Holt; Fish said Nelson has been cooperative in the investigation dealing with the tampering charges.

The Diemel's, from the Green Bay Wisconsin area, own a livestock company in their hometown and were in Braymer, according to Fish, to discuss "business" with Nelson, though Fish said the nature of that business is unclear other than it had to do with cattle. He said it appeared, it had been something the men had been communicating about for several months.

"We are not sure what happened during that business transaction," Fish said. "That is part of the investigation, that is ongoing and will be for some time."

Fish stated there has been law enforcement help from across the state to ensure that local law enforcement could work the case and still maintain staffing for other duties.

The search for the men continues on the Braymer farm and at other locations in the area. Recent rains have hampered law enforcement's ability to gather clues.

Nelson remains held with no bond. He is scheduled for another bond hearing on Aug. 1.