Saugus Police were called to 3 Alfred Road at around 4:30 PM on Saturday, to help with a "family member in distress," they said.
The DA's office said the officers were "confronted" by a 38-year-old woman, who was waving a knife at them, and one of the officers shot the woman three times.
They later identified the woman as Stephanie Gerardi, who lived in the Saugus home.
She was later pronounced dead on the scene after paramedics and officers tried to help her. None of the officers were injured.
WBZ-TV reported that neighbors were shocked, and that family of the woman who was shot came to the home to find out what had happened.
The officer that shot the woman was put on administrative leave as part of department policy, the D.A.'s office said.