My brother, the lawyer/public defender, told us something very disturbing on Thanksgiving Day. I'll start off with the conclusion: It's easier for a cop to shoot someone on the street legally than for a soldier in a war zone.
Soldiers have rules of engagement, usually quite strict. Apparently, all a cop has to say is that he feared for his life, and he is justified in using deadly force. Here in Ohio, we had some jackass of a cop jump on top of the hood of a (white) girl's car, and shoot her 4 times through the windshield. There were several passengers in the car when he did this. The car went out of control and crashed. What was this girl doing that cost her life, and endangered others? She was leaving a party, and refused to stop for an alcohol check. This could have happened to my niece.
The cop was just exonerated recently.
My brother's take is that the rules have to change. Otherwise murders by cop will continue, as well as the civil-unrest consequences.
I had a friend/coworker who was a marine. He met some girl, followed her back to Canada, and started working under the table for us because her brother was there. He once was saying how a lot of guys he was in the service with tried to go into law enforcement but it didn't often work out. Hiring boards, or whoever, are somewhat cautious because there's a very different skill set needed for a police officer when compared to a soldier in a combat zone. A few guys went all the way through with it and were now police officers and when they'd get together they'd remark how mind blowing the differences were in mentality. Like, it was the opposite of what the hiring boards were concerned with - the police officers had terrible discipline when dealing with suspects and the general public, while the guys just out of the military didn't for the most part. He thought a lot of it was because the military is so quick to discipline and court marshal while the police administration almost seemed to do anything to avoid disciplining officers, which is pretty much exactly what your brother said.
As for the militarization of the police force, I think it is a huge factor - not just the equipment, but the mentality they're trained with. I read somewhere (and have no idea how accurate it is) that over the last decade and a half or so the training has caused a mentality shift where every routine action is all of a sudden life or death. Every stop, every interaction, every incident could lead to their deaths and they act accordingly - and with excessive force - in many cases. Previously, there was a lot more faith in the general public and a lot more lenience, which resulted in a lot more incidents like this. Whatever I read went on for a while about this and it seemed to make sense.
I don't think the reasons behind it really matter. I mean, it could equally just be a case that we hear about it a lot more because almost every single person on the street has a device to record video on them at all times now. The thing is that it IS an issue and SOMETHING needs to be done. Cameras on police officers is a good step, but will it do anything? The garner is a perfect case - if you have a man being choked out to death on camera and no one is even indicted (not even convicted, indicted). The medical examiners office ruled it a homicide, it's on tape. The cops didn't even get suspended, just moved to desk jobs. The EMTs were suspended without pay for not responding fast enough - the police who actually were involved in killing this guy received no punishment. How fucked is that?
And that's the whole thing - there is increasing unrest and an increasing public perception that the police are untouchable. I don't know enough about the situation to say whether or not this cop should have been convicted, but should he have been indicted? Fuck yes. I don't know what evidence there is out there, but does the fact that there is clear video from two angles showing an officer breaking department regulations with the direct result being the death of a restrained man mean that he should be fired immediately? Fuck yes.
It makes a lot of people ask what it takes for someone to actually be punished. And sure, there are a lot of people out there who think that the police can do no wrong, but those people are idiots. It should be a no brainer that we hold the police to a higher standard of personal discipline and conduct than an average citizen, but for some weird fucking reason the powers that be seem to think it should go the other way. Something definitely has to change.