BILLINGS, Mont. >> Prosecutors on Friday filed murder charges and said they intend to seek the death penalty against two men accused of kidnapping a Montana teacher whose body was discovered in North Dakota two months after she disappeared.

Lester Van Waters Jr., 48, and Michael Keith Spell, 22, are accused of grabbing Sherry Arnold off a street in Sidney, Mont., on Jan. 7 while she was on a pre-dawn run.

Waters and Spell — who came from Parachute, Colo., looking for work in the booming Bakken oil fields — were arrested about a week after Arnold’s disappearance and originally charged with aggravated kidnapping.

An amended complaint filed by Richland County prosecutor Mike Weber on Friday charges each with one count of deliberate homicide and one count of attempted kidnapping. The aggravated kidnapping charge was dropped.

An affidavit filed in the case includes an alleged jailhouse confession by Spell that he choked Arnold and then held her face underwater to make sure she was dead.

Spell told another inmate he and Waters were high on drugs at the time and suggested the kidnapping came about because “Waters wanted to have sex,” prosecutors allege. The affidavit doesn’t say whether Arnold was sexually assaulted.

Previous court documents included a claim by Spell that Waters had choked Arnold in the back of his car. The new documents say she was killed almost immediately after encountering Spell during her run.

“Spell said Sherry Arnold was jogging on a path and he was walking approaching her,” the affidavit says. “Spell said Sherry said ‘Hi’ as they passed each other. Spell said he turned around and speared Sherry in the back of the head and knocked her down. Spell said he choked her out.”

Arnold’s body was not found until late March. Court documents filed Friday indicate it was Waters who led them to her shallow grave after Spell’s attempts to find the location were unsuccessful.

Her body was found along Highway 1804 near Williston, N.D., along a shelter belt, a line of trees used by farmers as a shield from the wind.

“Waters pointed to the approximate location of the actual hole where Arnold was buried,” the affidavit says. “A broken branch was resting over the hole. Waters advised Sherry Arnold was buried lying on her side in a fetal position. … Waters became emotional, cried and stated, ‘I didn’t kill that lady.”’

Weber, the Richland prosecutor, declined comment beyond what was in the court documents.

Telephone messages left by The Associated Press for the public defenders representing Spell and Waters were not immediately returned.

The two men were being held in the Richland County jail on $2.5 million bail for each. Because Arnold’s body was allegedly taken across the North Dakota state line, federal charges are also possible, although none have been filed.

The next hearing in the case is scheduled for May 31, with trials for the two men scheduled to start in July. However, the new charges could change that.

Arnold was a popular veteran math teacher at Sidney High School, where her husband, Gary, also worked and her two children attended school. She grew up on a ranch outside Sidney, a city of 5,000 near the confluence of the Yellowstone and Missouri rivers that’s been drastically changed by a recent oil boom.

Arnold’s kidnapping has raised concerns among Sidney residents about the changes overtaking their community with the influx of thousands of oil field workers. Concealed weapons permit applications have been soaring, authorities say, and residents of the close-knit town say they are now more suspicious of strangers.

Spell’s father, Harry, has told the AP that his son had traveled with Waters to the Bakken oil fields of Montana and North Dakota after Waters guaranteed work paying up to $2,000 a week working. Harry Spell said his son was anxious to prove himself to his parents and girlfriend Angel Cruz, with whom he has a 1-year-old son.

Angel Cruz declined to comment when reached by telephone Friday. A message left for Harry Spell through a family friend was not immediately returned.

Michael Spell had found past work in Colorado oil fields near Parachute and on a fire damage cleanup crew but was unable to keep the jobs “because he didn’t quite understand what to do,” Harry Spell said earlier. Harry Spell has said his son has an education less than a kindergartner.

Spell said in a February court appearance that he was illiterate and that his court-appointed attorneys had to read him the documents in which he was charged with kidnapping.

Waters is originally from Florida, where he has a lengthy criminal background and served time in state prison. Spell’s relatives say the younger man fell under Waters’ influence after the older man helped Spell and some of his associates get work as roofers.