One day after a grand jury declined to indict a New York police officer in the death of Eric Garner, prompting angry protests and calls for reform from elected officials, Mayor Bill de Blasio on Thursday announced the start of a significant retraining of the nation’s largest police force.

 “The way we go about policing has to change," de Blasio said.

Police Commissioner William J. Bratton said the retraining would require some 22,000 officers to complete a three-day course.

The program, beginning this month, is modeled on the periodic required firearms retraining that all officers must regularly undergo. Mr. Bratton first announced the department-wide retraining effort in the wake of Mr. Garner’s death. He provided further details at a City Council hearing in September, including learning “de-escalation” techniques, the New York Times reports,

On Thursday, First Deputy Benjamin Tucker provided a broad outline of what officers would be taught in each of the three days. The program — which includes teaching on street tactics as well as presenting a “nonjudgmental” posture — was a kind of “refresher” from what officers learn at the Police Academy, Mr. Bratton said.