A Washington state man has pleaded guilty in Montana to beating and stabbing his 3-year-old son to death last summer. In pleading guilty to deliberate homicide Tuesday in a Dillon, Mont., court, Jeremy Brent Cramer, 38, of Lacey, Wash., added his impending prison time does not matter because he no longer has his son, Broderick. "After a few months of thinking about it, I'm taking accountability for it," Cramer said Tuesday before admitting to killing the boy in a field near Anaconda, Mont. He had previously entered a not guilty plea. In court, Cramer did not describe the crime. Investigators located a knife and two blood-covered rocks near the boy's body, the (Butte) Montana Standard reported Wednesday. While incarcerated for homicide, Cramer admitted to the crime in a telephone call to his father, saying his truck ran out of gas and he began walking down a road with his son atop his shoulders. He then said he did not know why he beat his son, court records said. Cramer's family told authorities he is a drug addict known to go from doctor to doctor to seek medication. Investigators found an empty container for a generic substitute of the stimulant Adderall that Cramer filled five days before the incident, court records showed. Prosecutors said they seek a sentence of life imprisonment with no parole restrictions.