New York's mayor has admitted "something went horribly wrong" after a police sergeant shot dead an elderly woman with mental health problems.
Bill de Blasio said officers were supposed to use deadly force "only when faced with a dire situation" - and said it was "very hard to see that standard was met".
He admitted the fatal shooting in the Bronx was "tragic" and "unacceptable".
Police said they were responding to a 911 call about an emotionally disturbed person in a seventh floor flat on Tuesday night.
Officers claim when they arrived 66-year-old Deborah Danner was holding a pair of scissors, and Sergeant Hugh Barry persuaded her to drop them.
Ms Danner then grabbed a baseball bat and tried to strike the sergeant, who fired two shots and hit her in the torso.
She was taken to a hospital, where she was pronounced dead.
Mr de Blasio said police had been called to the victim's home several times before to take her to the hospital during psychiatric episodes.
He added that on each of those occasions she was taken away safely.
Police Commissioner James O'Neill said the sergeant did not follow department procedures and has been placed on modified duty.
He said the handling of the incident was "not how we're trained" and "it is clear in this one instance that we failed".
Investigators are now looking at why the sergeant did not use his Taser instead.
Bronx Borough President Ruben Diaz Jr has condemned the shooting.
He said: "This elderly woman was known to the police department, yet the officer involved in this shooting failed to use discretion to either talk her down from her episode or, barring that, to use his stun gun."
