GAITHERSBURG, Md. - An off-duty Montgomery County police officer shot and killed his son as the younger man stabbed the officer's wife at their home, police said Thursday.

The officer fired at his 25-year-old son on Wednesday night after he saw him attack the woman who was also the younger man's mother with a sharp object in an upstairs bedroom of the family's Gaithersburg home, said Capt. Jim Daly, a police spokesman. The woman was critically injured and later died at a hospital. She was 53. Police didn't say what the sharp object was.

"It's a tragic situation, unimaginable," Daly said.

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Daly said the officer, whose name has not been released, is a sergeant and patrol supervisor and 27-year veteran of the department. The 58-year-old officer has been placed on administrative leave, which is standard in cases when officers fire their weapons. Police have not yet confirmed whether the gun was the officer's department-issued weapon.

Daly said the family had been engaged in a domestic dispute prior to the incident, reports CBS DC.

"The challenge we have here is there were only three people in the house," Daly said. "We don't have anyone else."

Police say they will release more information after other family members have been notified.

Neighbot Billy Walchalk described the family involve din the incident as “the nicest people you’d ever want to meet,” reports the station.

“They’re very talkative, very supportive of this neighborhood,” said Waclchalk. “We’re devastated by it.”

The couple reportedly also has two daughters who were not home during the incident.