Won't you please come to Chicago, show your face

Ex police chief Joseph McNamara addressed this dynamic in this op-ed:

Simply put, the police culture in our country has changed. An emphasis on "officer safety" and paramilitary training pervades today's policing, in contrast to the older culture, which held that cops didn't shoot until they were about to be shot or stabbed. Police in large cities formerly carried revolvers holding six .38-caliber rounds. Nowadays, police carry semi-automatic pistols with 16 high-caliber rounds, shotguns and military assault rifles, weapons once relegated to SWAT teams facing extraordinary circumstances. Concern about such firepower in densely populated areas hitting innocent citizens has given way to an attitude that the police are fighting a war against drugs and crime and must be heavily armed.

Yes, police work is dangerous, and the police see a lot of violence. On the other hand, 51 officers were slain in the line of duty last year, out of some 700,000 to 800,000 American cops. That is far fewer than the police fatalities occurring when I patrolled New York's highest crime precincts, when the total number of cops in the country was half that of today. Each of these police deaths and numerous other police injuries is a tragedy and we owe support to those who protect us. On the other hand, this isn't Iraq. The need to give our officers what they require to protect themselves and us has to be balanced against the fact that the fundamental duty of the police is to protect human life and that law officers are only justified in taking a life as a last resort.