KSTP

"We're working closely with the family to determine the circumstances that led to the stabbing," said Police Chief Scott Boerboom at a press briefing at Minnetonka City Hall on Sunday afternoon.

They found the 16-year-old with a life-threatening stab wound to the chest. The teen was transported to North Memorial Hospital, where he was pronounced dead.

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"We have a family that was torn apart by this tragedy," Boerboom said.

The 12-year-old, who was uninjured, was transported to the hospital for mental evaluation. Boerboom said he is with family and not in custody.

Police have not identified the 12-year-old or his older brother, because they are minors. According to Boerboom, the 12-year-old also has a twin.

Police said the boys' mother and other family members were home at the time of the incident.

"It's still early, we know some sort of altercation between the two boys occurred that's as much as I know right now," Boerboom said when asked what set off the incident.

Boerboom said this is the first time officers had been called to the family's apartment on a domestic violence complaint.

The Hennepin County Medical Examiner will do an autopsy and determine the exact cause and nature of the teen's death and make a positive identification.