A somber Mayor Bill de Blasio told reporters that the NYPD fatal shooting death of a 66-yearold mentally ill woman from the Bronx “should never have happened,” citing the incident could have been avoided.

And the questions kept coming: Why was a gun used over a Tazer, which the officer had? Why wasn’t Emergency Services Unit, which handles the mentally ill, brought in?

“It’s not for lack of training,” de Blasio told reporters at a news conference that focused on the shooting. “There were decisions made that should have been made differently.”

De Blasio condemned the actions of the shooter, NYPD Sgt. Hugh Barry, telling reporters justice will be sought.

His bottom line: protocol was not followed in this case involving the mentally ill. A full investigation is expected in the shooting that prompted NYPD Commissioner James O’Neill to declare the police “failed” in following standard protocol. “That’s not how it’s supposed to go. It’s not how we train,” O’Neill told reporters shortly after a scheduled breakfast.

The shooting happened just after 6 p.m. on Oct. 18 at 630 Pugsley Ave. in the Castle Hill section of the Bronx, police were called to answer reports of what they term an emotionally disturbed person. Sgt. Barry, responding to the scene, saw Deborah Danner holding a knife. After ordering her to put it down, Danner went for a bat. Jennifer Danner, the victim’s sister and legal guardian, stood outside a hallway when she heard a shot. Danner was rushed to Jacobi Medical Center and died of her wounds. Barry, meantime, was stripped of his gun and badge and placed on modified duty.

The shooting bore the hallmarks to the infamous Eleanor Bumpurs shooting of 1984, when an officer fatally shot Bumpurs, an elderly woman with a history of mental illness, after she allegedly lunged at the officer with a pair of scissors.

These days, the NYPD’s Emergency Services Unit is required to respond to confrontations involving the emotionally disturbed. Danner was known to have suffered from schizophrenia. “[Had] the Emergency Services Unit had been given the opportunity to do what they are specially trained to do I am very certain there would have been a different outcome,” de Blasio said.

Elected officials have called for a thorough investigation. Assemblyman Luis Sepulveda, a legislator representing the Castle Hill section, said he “would question why the sergeant who was armed with a Taser was unable to use it, but we were not there.  Again, I urge calm while the investigation proceeds.”

Bronx Borough President Ruben Diaz Jr., suggesting excessive force was used, also uttered the call for an investigation. “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,” Diaz said in a statement. Diaz’s father, Sen. Ruben Diaz Sr., representing Castel Hill in Albany, held a vigil for Danner the following day.

The shooting happened within the 43rd Precinct, which has seen a modest drop in crime over the last few months. It’s a precinct with a Neighborhood Coordination Officer program, which keeps a group of officers under one sector, embedding them in a neighborhood on the hopes of getting to know the communities and residents who live there. It’s unclear whether NCOs knew Danner.

Hours after the incident, de Blasio spoke over the phone with the victim’s sister and legal guardian, Jennifer, who stood at the hallway hearing the gunshot.

He told reporters “she did not in any way expect to hear shots to ring out” after the police responded to the incident. “It was a very painful conversation to say the least,” de Blasio said.