MEDFORD, Ore. – A 12-year-old boy is suspected of fatally stabbing his mother and wounding his sister.

Police responded to two 911 calls on Tuesday and found the boy’s 52-year-old mother at the family’s home in Ashland, the Mail Tribune reported.

The boy’s sister was in stable condition at a hospital and was expected to survive.

The boy doesn’t have a history of crime or a troubled past, Ashland police Chief Tighe O’Meara said.

O’Meara said it’s unknown what sparked the stabbing and that investigators are going to speak with friends of the children.

“It’s going to take a while,” O’Meara said. “I would imagine detectives would be working on this for several days to maybe a couple weeks.”

He said the district attorney will determine how the boy will be charged.

“Every homicide is tough, and to watch this unfold and see a 12-year-old taken into custody … it’s been a rough day and it’s going to be a rough patch for the community to work through,” O’Meara said during a news conference. “This is really especially tragic.”

One other family member who was home at the time was not injured.

Tuesday was the first time police were called to the home.

“This was completely out of the blue,” O’Meara said.

Online records said the mother was retired from the Air Force and had earned degrees in aeronautical engineering and engineering management.