A cancer-stricken mother allegedly killed her 29-year-old son in his sleep and buried his body in a pit with sheep heads to settle a feud over who should inherit the family’s $3 million ranch in Colorado, authorities said.

Deborah Sue Rudibaugh, 68, confessed in July to killing her son, Jacob Henry Millison, and burying his body by herself more than two years earlier, according to court records in Gunnison County obtained by the Denver Post.

But investigators at the time considered Rudibaugh’s confession to be an attempt to shield her daughter and son-in-law from being connected to the gruesome murder.

The Grand Junction Daily Sentinel reported that Rudibaugh, of Parlin, was arrested on first-degree murder charges in Grand Junction on Friday, one day after her daughter, Stephanie Jackson, 33, was arrested on the same charge. Investigators believe Jackson killed her brother in order to gain control of the family’s 700-acre ranch in Quartz Creek Valley.

Jackson’s husband, David Jackson, 34, was also arrested Tuesday on charges of accessory to first-degree murder and tampering with the body of Millison, the Denver Post reported. All three remain held in the Gunnison County jail.

The family, according to arrest warrant affidavits obtained by the newspaper, was quarreling over an inheritance from Rudibaugh’s second husband, who left behind sums ranging from $35,000 to $45,000 to four children from his first marriage and $30,000 to Stephanie Jackson.

Rudy Rudibaugh, who died in 2009, left the ranch to Deborah Rudibaugh in his will. The Jacksons then returned to the ranch in 2012 after renting out their Denver home.

Millison filed for a restraining order against David Jackson after he pulled a gun on him in January 2013. Millison later disappeared in May 2015, leaving his vehicles and dog, Elmo, behind at the ranch. An investigation into his disappearance was later launched after several people filed missing-person reports.

Rudibaugh then claimed to investigators that her son went on a motorcycle trip to California and hung with an unpredictable group of friends while he used drugs ranging from cocaine to steroids. She also claimed he took with him a book called “How to Disappear Without Leaving a Trace,” the Denver Post reports.

Rudibaugh later told police Millison “deserted” the family after she tore up a will that split the ranch between him and his sister, replacing the document with a will that left everything to her.

One month later, in July 2015, Rudibaugh admitted killing her son and took deputies to the spot where she said she buried him after claiming he tossed her in a ditch and threatened to kill her if she didn’t authorize a new will excluding the Jacksons.

Rudibaugh, who is now battling breast cancer, told investigators she shot her son in the head as he slept and later wrapped the body in plastic before using her “Yankee ingenuity” and a front-end loader to bury his body in a pile of horse manure in a livestock pen. Rudibaugh said she later moved the body to protect it from being disturbed by animals.

Rudibaugh, according to the affidavit, said she planned to leave behind prior to her death a letter detailing why she killed her son and where authorities could locate his body.