MISSOULA, Mont. — A 38-year-old Montana man pleaded guilty to two counts of deliberate homicide for killing his former landlord and a Missoula motel worker in what authorities said was a meth-fueled, cross-state crime spree last December.

Scott Austin Price, a transient from Billings, entered the plea Monday to fatally stabbing 78-year-old Ed Martin in Miles City on Dec. 14.

Helen Martin told investigators that Price had stopped by to look at a camper they were selling. A short time later, she said, Price came back to the house, assaulted her and tied her up. She was able to escape and call for help. Ed Martin’s body was found in the trailer.

On Tuesday, Price acknowledged stabbing a 68-year-old woman in the stomach outside a Missoula grocery store on Dec. 21, then going to a nearby hotel and killing 56-year-old Lonette Keehner and stealing her car.

Price and his co-defendant, Sarah McKnight, were arrested the next day in Idaho, where Keehner’s car was recovered.

Price told officers in Idaho that he and Martin were in a trailer arguing over a sales price when Martin hit him with a flashlight. Price told officers he grabbed a knife and stabbed Martin in the neck, charging documents state.

Price, who also pleaded guilty to the aggravated kidnapping of Helen Martin, stole a pickup and $4,000 from a safe, court records said.

He attributed his actions to methamphetamine use, prosecutors said.

McKnight told investigators that she met up with Price in Great Falls and they drove to Missoula in her car, but decided they needed a better vehicle and more money. They had planned to kidnap someone, steal their car and take their debit cards, she said.

McKnight pleaded guilty in May to several felonies — including deliberate homicide — for her role in the Missoula crimes. She has not been sentenced in that case and is serving time at the Montana State Prison for a 2014 burglary in Powell County.

Price is scheduled to be sentenced on Dec. 5 in Miles City and on Dec. 12 in Missoula.