Scott Hacking told The Salt Lake Tribune that it was to him and their brother, Lance, that Mark confessed on July 24, five days after Mark Hacking reported his wife, Lori, missing.
"My brother and I sat and hugged him for about an hour, and then we went home," Scott Hacking said. The information was relayed to police through an intermediary the following day. A police affidavit said a "reliable citizen witness" revealed the confession to authorities.
Mark Hacking, 28, called police July 19 and said his wife had failed to show up for work after going for an early morning jog.
He was arrested Monday on suspicion of murder as he was about to be released from the psychiatric ward where he'd been since being found naked outside a hotel July 20.
Police believe that three days before she vanished, Lori Hacking discovered that her husband had not been enrolled in a North Carolina medical school where the couple was packing to move. It also was discovered that he had lied about graduating from the University of Utah.
Late Thursday afternoon was the deadline for Salt Lake County District Attorney David Yocom to file formal charges, but he has said he might not be ready and might ask the court for an extension.
Yocom has declined to say whether he would seek the death penalty, but did say the wishes of the victim's family are given great weight in such decisions.
Scott Hacking, 33, said he was aware that his brother, if convicted, could face execution.
"I certainly worried about that," he told the newspaper. "My family believes in the justice system... If those consequences are the ones he has to face, then again, we will support him through that point, though I hope he does not have to face that consequence."
He said he hopes the information resolves the case.
"My family started this entire process with two goals in mind," he said. "One was to bring Lori back and the other was to discover the truth. And we were determined to do both of those things.
"No brother wants to offer information about his own brother," he said.
The search for remains at the county landfill resumed Wednesday night. The searches have been halted temporarily when cadaver dogs were needed on other assignments and when their handlers felt the animals needed time off.
Large spotlights lighted the area Wednesday night and a backhoe tore out large chunks of garbage that were then spread out for the dogs to go over. The searches are conducted overnight because the dogs work more effectively in the cooler air, authorities have said.