A teenager was arrested on Thursday after his two younger brothers, ages 4 and 10, were found stabbed to death at the family’s home in West Point, Utah, Wednesday night, police said.

Davis County Sheriff Todd Richardson said the 15-year-old suspect appeared to work alone and is being held at the Farmington Bay Youth Detention Center.

“The manner of death appears to be consistent with penetrating knife wounds, however, the official cause of death will be determined by the Medical Examiner’s Office,” Richardson said in a media release.

The 15-year-old had been left in charge of the younger boys while their mother was out with some of her other children.

The boys’ mother called the Davis County Sheriff’s Office at 7:36 p.m. after she returned home and found her 4-year-old son was dead. She reported that her 10- and 15-year-olds were missing.

Officers searched the house and found the 10-year-old’s body. The eldest brother wasn’t located until shortly before midnight. He appeared to be in good condition, but was taken to the hospital for evaluation, police said.

The case is being investigated as a homicide. The county attorney’s office is working with authorities on whether to charge him as an adult or a juvenile.

Officials are deciding whether to charge the suspect as an adult or a juvenile.

The suspect’s name, which was originally reported by local papers, is being withheld because he is a minor. He had been placed in charge of the younger boys while their mother took some of her other children to a dance recital, the Salt Lake Tribune reported.

Lindsey Caballero, a neighbor and family friend, told the Associated Press that the 15-year-old was the couple’s oldest and biological son. The couple had had six children, four of whom were adopted, including the victims.

The father was away on active military duty and has reportedly been notified.