Police "failed" a 66-year-old woman with a history of psychiatric problems when an officer shot and killed her Tuesday night, said New York City Police Commissioner James O'Neill.
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A uniformed NYPD sergeant shot and killed Deborah Danner after she wielded scissors and a bat at him while he was checking up on her, police said.
O'Neill said police were "were called to help" a "person in crisis."
"That's not how it's supposed to go," O'Neill said. "It's not how we train. Out first obligation is to preserve life -- not to take a life when it can be avoided."
Sgt. Hugh Barry responded to a 911 call about an emotionally disturbed person in The Bronx just after 6 p.m., when a neighbor complained that a woman was acting in an irrational manner, according to the NYPD.
About 10 minutes later, Barry entered the apartment to investigate and found Danner armed with a pair a scissors, according to cops. The sergeant convinced Danner to put the scissors down, but she then approached the officer and grabbed a baseball bat, police said.
The sergeant fired two shots from his revolver as Danner attempted to strike him with the baseball bat, police said. She was struck in the torso and transported to Jacobi Medical Center, where she was later pronounced dead.
O'Neill said that while "in the vast majority of cases we get it right," he wants "to know why it happened."
"Cops know when you become a police officer you are 100 percent accountable for your actions -- everything you do," he said. "When a life is taken, as one was last night, we have to ask tough questions."
The NYPD has launched an internal investigation into the incident, police said. Barry has been put on modified duty as the department tries to determine why he used deadly force instead of his Taser.
New York City Mayor Bill de Blasio called the police-involved shooting "tragic" and said it "should not have happened." The mayor also said that Barry did not follow his police training but added that until last night, the NYPD had properly handled nearly 200 calls in 2016 involving an emotionally disturbed person.
The Sergeants Benevolent Association said: "Being forced to shoot a civilian under any circumstances is traumatic for police officers, but to be immediately vilified based on innuendo and the social and political climate only compounds the tragedy."
ABC News' Aaron Katersky contributed to this report.