An investigation is underway after authorities say a Winchester, MA, police officer fatally shot a knife-wielding man inside an apartment on Monday.

A security guard for the Parkview Apartments on Swanton Street called 911 just after 8 p.m. to report that a resident of the building, a 35-year-old man, had reported an issue within his unit, Middlesex District Attorney Marian Ryan and Winchester Police Chief Peter MacDonnell said in a joint press release.

Three Winchester police officers responding to the unit. In the apartment they reportedly found a man holding two knives, WHDH reports.

The officers gave verbal commands for the man to drop the knives before a Taser was deployed twice, which was unsuccessful in subduing the man, according to Ryan and MacDonnell.

The man continued to approach the officers while still holding the knives and one of the officers fired his service weapon, striking the man, Ryan and MacDonnell said.