NEW YORK — After two officers were fatally gunned down through the window of their squad car in 2014, the nation’s largest police force embarked on an ambitious plan to outfit all of its squad cars with inch-thick bullet-resistant glass and armored door panels capable of stopping a round from a .44 Magnum.

But that ongoing effort does not cover the RV-like mobile command posts like the one in which a New York Police Department officer was shot to death through an ordinary window early Wednesday. Some are now questioning that decision, especially since such mobile command posts, which are often planted in neighborhoods for weeks, might actually be more vulnerable.