RITZVILLE, Wash. -

Washington's Attorney General confirmed Tuesday his office has obtained a guilty plea from a man charged with bludgeoning his girlfriend to death in front of their three-year-old son during a cross-country road trip that ended in Adams County.

Manuel Argomaniz-Camargo pleaded guilty to first-degree murder with a deadly weapon enhancement and possession of methamphetamine in relation to the killing of Ana Montelongo Garcia, whose body was found next to their abandoned car along I-90 near Ritzville in March.

His sentencing is scheduled for Oct. 4 in Adams County Superior Court in Ritzville, where Attorney General Bob Ferguson's office is seeking the top end of the sentencing range of 27 years and 9 months plus an additional two years for the deadly weapon enhancement.

“Keeping our communities safe from violent offenders is one of my top priorities,” Ferguson said. “Today’s guilty plea holds the defendant accountable for his horrible crime, brings a measure of justice for the victim, and spares her family the ordeal of a trial.”

The Attorney General's Office prosecuted the case at the request of the Adams County Prosecutor's Office.