A 14-year-old boy has been arrested this week on suspicion of killing his parents and critically injuring his younger sister in rural Fresno County, authorities said.

The boy, whose name has not been released because he is a minor, faces two charges of murder and one charge of attempted murder, the Fresno County Sheriff’s Office said in a news release. Detectives have not determined a motive in the case.

The boy’s parents, Lue Yang and Se Vang, both 37, were found dead by officers in the family’s Miramonte home around 7:40 p.m. Wednesday, authorities said in the release. The boy’s 11-year-old sister “suffered major injuries” but is expected to survive.

The boy placed a 911 call earlier to report that someone had broken into his home and attacked his mother, father and sister, then fled in a pickup truck, according to the news release. Detectives who spoke with the boy discovered “inconsistencies” with his story, determining he fabricated the story and had used “multiple weapons to attack his family members,” authorities said.

A 7-year-old boy was also home during the attack, but was not physically injured, authorities said. Other family members are now caring for the boy.

Officers had not previously received any calls for service to the family’s home, Fresno County Sheriff John Zanoni said during a news conference this week.