The 11-year-old Centennial boy accused of killing his 5-year-old brother has been formally charged with first-degree murder, according to the Arapahoe County District Attorney’s Office.

The formal charge was filed Monday in addition to an aggravated juvenile offender charge, according to Eric Ross, a spokesperson for the District Attorney’s Office. Ross said the boy has not yet been advised of the charges against him.

The boy was arrested on March 10 after Arapahoe County sheriff’s deputies were called to a home in the 5200 block of South Jericho Way at about 5:30 p.m. At the home, a 5-year-old boy was found dead.

After the boy was identified as a suspect and arrested, he was placed into custody at the Marvin W. Foote Youth Services Center in Centennial. Due to the boy and the victim being minors, police have yet to release their names.

Under Colorado law, a minor must be at least 12 years old to be tried as an adult. A child under 10 cannot be charged criminally. Ross said the case is being heard in juvenile court.

A first-degree murder charge in Colorado indicates premeditation and intent to cause an individual’s death.

Defense attorneys who spoke to The Denver Gazette last week said it is rare for someone so young to be charged with first-degree murder and questioned if someone so young can understand what a first-degree murder charge is.

The 5-year-old boy was a kindergarten student at Timberline Elementary School, according to a letter sent to parents by the school’s principal. The school district is providing mental health support to students, according to a district spokesperson.

If convicted of first-degree murder as an aggravated juvenile offender, which would include a sentencing enhancer, the 11-year-old would face a minimum of three years in Colorado Division of Youth Services detention, and up to seven years.