The number of murders in New York City has dropped to what years ago would have seemed like an impossible low: 328 killings recorded in 2014, the lowest figure since at least 1963, when the Police Department began collecting reliable statistics.

With hours left in 2014, the number of murders capped a year of lower numbers in nearly every major crime category and offered an answer to what had been a central question of Mayor Bill de Blasio’s first year: Could a mayor elected on promises of police reform keep the specter of the bad old days from returning?

But there is little celebration among the city’s police officers, who remain in mourning after the recent killings of two comrades. They have also heard calls to reverse their policing practices and found their union representatives locked in a bitter public struggle with the mayor that, in recent days, has coincided with a substantial drop in enforcement of everyday crime by officers.

Reports of major crimes citywide continued their yearlong decline, to 105,428 through Dec. 28, from 110,728 in the same period in 2013, according to Police Department statistics. Murders dropped from 335 in 2013.