( CNN ) -- An off-duty police officer shot and killed his son in the family 's Maryland home because the younger man allegedly was stabbing his mother , who later died , Montgomery County Police said Thursday . Police identified the deceased as Denise Stirkens , 53 , and her son , Christopher Stirkens , 25 . James Stirkens , 58 , who 's been working at the Montgomery County Police Department for 27 years , is a patrol sergeant in Silver Spring and has been placed on routine administrative leave , police said . Authorities did n't immediately have any background information on the son , police said . The incident occurred about 8 p.m. Wednesday in the family 's Gaithersburg home when an altercation arose between the mother and the son , Montgomery County police Capt . Jim Daly said . The father found his son attacking his mother with a sharp object , and the officer shot his son with a handgun , killing him at the scene , Daly said . The mother later died in the hospital , police said . Daly did n't immediately know whether the officer 's service weapon was used in the shooting . In addition to the son , the couple also has two daughters , who were n't in the family home . The son lived in the home , police said . The investigation continues ; no charges had been filed as of Thursday , police said .
NEW : Dead are Denise Stirkens , 53 , and son , Christopher Stirkens , 25 , police say . NEW : James Stirkens , 58 , a patrol sergeant , is put on routine administrative leave . An off-duty police officer shot and killed his son in the family home . The son was allegedly stabbing his mother , who later died in the hospital .