The fifth-grade boy told investigators he and his friend had planned to kill a former girlfriend because she was "rude" and "always made fun" of him and friends, according to court documents.
Prosecutors said he pleaded guilty last month to all charges. They plotted to entice the fifth-grade girl away from their elementary school, the court papers stated.
The 10-year-old had taken a functional Remington Model 1911 pistol that originally belonged to his grandfather from his older brother’s room, according to court records.
The boys had also packed ammunition and a knife, but they were stopped on Feb. 7 shortly after they boarded a school bus.
A fourth-grade student spotted the knife and reported it to a teacher’s aide. The names of six other targeted classmates were on a list the boys had, Stevens County prosecutor Tim Rasmussen said.
Stevens County Superior Court Judge Allen Nielson sentenced the boy to a minimum of just over three years in juvenile detention and a maximum of nearly 51/2 years, Rasmussen said.
An 11-year-old boy accused of joining in the plot is charged with conspiracy to commit first-degree murder, possession of a dangerous weapon in the form of a knife at school and tampering with a witness, Rasmussen added.
The 11-year-old suspect faces a court hearing later this month.
The 10-year-old boy will serve his sentence at the Echo Glen children’s juvenile center in Snoqualmie, Wash., 70 kilometres east of Seattle.
He has already spent 97 days in a local juvenile detention facility, Rasmussen said.