Wexler said New York City shows how training can reduce fatal police shootings.

In 1971, the city had 314 officer-involved shootings, 93 of which were fatal, he noted.

The next year the city passed a law prohibiting officers from shooting into vehicles, a practice still permitted by many police departments.

Within two years the city reduced police shootings to 121, with 41 fatal. By 2015, after a period when crime dropped enormously, the number had fallen to 23 people shot by police with eight killed. No New York City police officers have been seriously hurt by someone in a car in the 46 years since the ban in shooting into vehicles took effect, he said.