Because cops are ultimately cowards. They kill people in cold blood, but they only have that bravado because they know most people are never going to throw their lives away trying to stop them. Cops are not skilled marksman or particularly brave. They just operate in an environment where they can use force on people, but no one will ever use force back on them. This is why they act like such assholes. They’ll escalate situations. They’ll introduce violence to scenarios where none was previously present. They’ll demonstrate extreme aggression…but only so long as they believe they’re perfectly safe. How often do you hear about a cop beating someone, and a random uninvolved passerby just pulling out a gun and blowing their head off while they’re in the act of brutalizing someone? It never happens. People aren’t willing to throw their lives away to rescue others from police violence. So cops can victimize people with impunity.

Except, once in awhile they run into someone that IS willing to throw their life away. A school shooter is clearly willing to shoot at cops. If you’re willing to kill kids, you’ll certainly be willing to kill a cop. When they actually face the chance of someone fighting back, they run like the cowards they are.

Brave people don’t become police officers. People looking to have power over others become police officers.