Mayor Bill de Blasio and his police commissioner sharply criticized an NYPD sergeant who fatally shot a mentally ill Bronx woman in her home, with the mayor calling the killing "unacceptable." NY1's Dean Meminger filed the following report.

A blunt admission by Police Commissioner James O'Neill.

"What is clear in this one incident, we failed," he said.

O'Neill said Deborah Danner should have beeen saved by police, not killed. 

"We had a woman, a person in crisis, where we were called to help. We ended up taking the life of 66-year-old Deborah Danner. That's not how it's supposed to go," he said.

Tuesday evening, a 911 caller said Danner, who has a history of mental illness, was acting violently. 

When Sergeant Hugh Barry arrived at her Bronx home, he convinced Danner to put down scissors she was holding. But when she grabbed a bat and tried to hit him, he fired two shots, killing her.

O'Neill says police had been called to her apartment many times before, and that it appears Barry failed Tuesday to keep a safe distance as NYD training calls for in dealing with emotionally disturbed people. 

"Our policy is isolate and contain," O'Neill said. "If you have somebody in a certain area and time is on our side, ESU is dispatched to every DP job, so we had time.

Mayor Bill de Blasio said Danner "should be alive right now, period," and that he phoned Danner's sister to apologize. 

"There was obviously the option of using a Taser, that was not employed," de Blasio said. "We will fully investigate this situation, and we will cooperate fully with any prosecutorial agencies. But we need to know why this officer did not follow his training." 

The sergeants' union said O'Neill was wrong to quickly strip Barry of his gun and place him on modified duty, adding, "Incidents like this one evolve in a matter of minutes, perhaps even seconds....to be immediately vilified based on innuendo and the social and political climate only compounds the tragedy." 

Barry and other officers were sued for excessive force five years ago after clashing with concertgoers in Manhattan. A jury ruled in the officers' favor. 

The Rev. Al Sharpton called O'Neill's comments "good and responsible" but said the shooting shows there needs to be systematic change in the NYPD.