Two people are dead in a tragic family incident in Gaithersburg, Md., where Montgomery County police say an off-duty officer shot and killed his son while trying to defend his wife from the son’s stabbing attack.

Capt. Jim Daly told the Gaithersburg Gazette that 58-year-old officer James Stirkens — a 27-year veteran of the police force — discovered his 25-year-old son, Christopher Stirkens, attacking his mother and James’s wife, Denise Stirkens, in an upstairs bedroom.

“He observed his son attacking his wife with a sharp instrument,” Daly said.

To defend his wife, Stirkens shot his son, killing him, Daly said.

Fire and rescue personnel took 53-year-old Denise Stirkens, to a local hospital, where she died.