An Idaho man has been sentenced to a lengthy prison term for the gruesome murder and dismemberment of a man he had been stalking. The perpetrator, Alan Douglas Bruce, 70, allegedly sent a letter to the victim’s daughter claiming he did her a favor by dismembering the body to save on funeral expenses.

Bruce was sentenced to 20 years in prison after pleading guilty to second-degree murder and evidence destruction in the case of 47-year-old Patrick Shelton, according to court documents. The Custer County Sheriff’s Office launched an investigation on May 10 when Shelton did not return from a wood-cutting trip.

According to an arrest affidavit obtained by Boise’s NBC affiliate KTVB, police discovered Shelton’s truck near Big Hill on Forest Service Road 256. Inside the vehicle was Shelton’s dog, but Shelton himself was missing. Investigators found blood spatter and what was believed to be brain tissue inside the truck.

The detectives reported that the blood was spread throughout the front interior, and brain matter was spotted on the rearview mirror. Additionally, Shelton’s hair was found on the windowsill, and a piece of mail addressed to Bruce was located on the road next to the vehicle.

Shelton’s hair was also recovered on the windowsill. In the road next to the truck was a piece of mail addressed to Bruce, the affidavit said.

Phone records showed Shelton was on Bruce’s property between approximately midnight and 9 a.m. on May 8. Bruce was then brought in for an interview and initially denied any knowledge of Shelton’s whereabouts. Meanwhile, investigators searched Bruce’s property.

According to the affidavit, detectives discovered possible bone fragments and broken glass behind a pickup truck. They also found “small flecks of human flesh” and red human hair — the same color as Shelton’s — next to Bruce’s camper. Police dogs indicated there were human remains in several areas of the property.

In a second interview, Bruce told investigators that he was going to prison for a “long time,” the affidavit said. Bruce said he and Shelton were involved in a traffic accident. The defendant left the area and returned with an AR rifle. Using the “cover of darkness,” he watched Shelton for “hours” from afar with night vision binoculars, detectives wrote.

At one point, Bruce said he approached Shelton armed with the rifle and asked, “Do you want some of this?” Bruce claimed Shelton was armed and responded by saying, “You better pull the trigger motherf—er” before pointing the gun at him.

“When that 45 came up it was me or him,” Bruce told detectives.

Bruce shot Shelton dead. He then proceeded to dismember Shelton’s body with a chain saw before burning the remains in a barrel. Bruce loaded the barrel into his truck, drove to a bridge and threw it into a river. He also disposed of the murder weapon and Shelton’s gun. Once he returned home, he cleaned up the scene with bleach and a Shop-Vac before towing Shelton’s truck to the Big Hill area.

When asked why he didn’t call cops, “Bruce said you ‘shoot, shovel and shut up,’” the affidavit said. Bruce also showed deputies a picture of Shelton’s body, which sat inside the victim’s truck. It was taken shortly before 6:30 a.m. on May 8.

The affidavit did not explain why Shelton was on Bruce’s property, nor did it detail his exact relationship with Bruce, though the defendant said the two were friends.

Local ABC, CBS and Fox affiliate KIFI attended Bruce’s sentencing hearing on Monday, where two of Shelton’s daughters made victim impact statements. One of the daughters reportedly said she received a disturbing letter from Bruce that said he did them a favor by dismembering and disposing of the body because they could save on funeral costs. Authorities have never recovered Shelton’s body.

Bruce was reportedly defiant during the hearing, first trying unsuccessfully to withdraw his plea and then claiming he shot his buddy Shelton in self-defense.