A special grand jury will be convened to investigate the fatal police shooting of Deborah Danner in the Bronx, District Attorney Darcel Clark announced on Monday.

The grand jury will be tasked with determining whether criminal charges should be brought against the NYPD sergeant who fired the fatal shots.

“I have pledged to the people of the Bronx to conduct a thorough, fair investigation into this matter and I believe that presenting the evidence to a grand jury will best accomplish that goal,” Clark said in a statement.

Danner, 66, was shot and killed inside her Pugsley Avenue apartment in Castle Hill on Oct. 18 after police said she attempted to strike the sergeant with a bat. She was pronounced dead at Jacobi Medical Center.

The sergeant, who was identified by a law enforcement source as Hugh Barry, was placed on modified duty.

Danner was known to the NYPD as having mental health issues and police had been called to the apartment on previous occasions. All of those incidents had ended peacefully, police said, with Danner agreeing to be taken to a hospital for treatment.

The shooting drew immediate condemnation from Mayor Bill de Blasio and other local officials. De Blasio had called Danner’s death “unacceptable” and said police were investigating why the sergeant didn’t follow protocol for de-escalation or use his stun gun instead of his weapon.

“It is important to determine exactly what happened in this tragic incident,” Clark said. She also warned, however, that there would be “no timetable for the grand jury to be impaneled or for it to reach a determination.”