I think there's a pretty stark difference between a suspect with a weapon in their hand, and pretty much all other suspects. What continuely shocks me and pisses me off is how many people die to the police that are unarmed and/or handcuffed.
In my life, in one instance, I've had about 15 or so cops all pointing weapons at me at the same time. This was back in the 90s, when you didn't die immediately in situations like that. And what I remember most about that moment was watching the muzzles of their guns drifting and shaking as these guys were pumped with adrenaline, expecting a shootout and getting 4 teenagers in a gas station parking lot, legally exercising their right to shoot a car they owned with guns. I remember thinking "Holy fuck, if we do just one thing wrong, these guys will fucking waste us." Turns out someone did do something wrong, and no one got shot, but still. I didn't see cops as these cool, controlled operators in command of the situation. I saw a lot of middle-aged white guys in the dead of night, very scared or totally excited or both. If that situation played out today, there's an excellent chance someone would have died that night.
So my general take on cop-related homicides of the last decade plus is this: cops are scared. Really, really scared. 9/11 fucked everyone up, and suddenly every cop thinks and trains like a soldier now. It's puerile to say it, but cops act are and equipped like they'll be fighting Muslim Extremists in the streets any day. For the last fucking 13 years.
Add to that a lot of roadside shootings during garden variety traffic stops, and now survivalist nuts fulfilling law enforcement's worst nightmares/fantasies, and cops are basically expecting an armed conflict at every interaction and stop until it's been proven not to be the case. And that's just your average cops. Never mind the truly bad apples, the violent psychopaths with a badge, the racists, the poor hires and underqualified rookies. And then there's the hero complex that gets dump on top of all that, because of the constant media and political treatment of law enforcement and "civil service" since 9/11.
And now here I am, violating what I'd just said a couple pages ago about restraining my urge to jump into internet debates. >< It's a long path, dat e-lightenment.