As a kid, I got used to being stopped by the police. I grew up in an inner-ring suburb of St. Louis. It was the kind of place where officers routinely roughed up my friends and family for no good reason.

I hated the way cops treated me.

But I knew police weren’t all bad. One of my father’s closest friends was a cop. He became a mentor to me and encouraged me to join the force. He told me that I could use the police’s power and resources to help my community.

So in 1994, I joined the St. Louis Police Department. I quickly realized how naive I’d been. I was floored by the dysfunctional culture I encountered.

I won’t say all, but many of my peers were deeply racist.

One example: A couple of officers ran a Web site called St. Louis Coptalk, where officers could post about their experience and opinions. At some point during my career, it became so full of racist rants that the site administrator temporarily shut it down. Cops routinely called anyone of color a “thug,” whether they were the victim or just a bystander.

This attitude corrodes the way policing is done.

As a cop, it shouldn’t surprise you that people will curse at you, or be disappointed by your arrival. That’s part of the job. But too many times, officers saw young black and brown men as targets. They would respond with force to even minor offenses. And because cops are rarely held accountable for their actions, they didn’t think too hard about the consequences.

Once, I accompanied an officer on a call. At one home, a teenage boy answered the door. That officer accused him of harboring a robbery suspect, and demanded that he let her inside. When he refused, the officer yanked him onto the porch by his throat and began punching him.

Another officer met us and told the boy to stand. He replied that he couldn’t. So the officer slammed him against the house and cuffed him. When the boy again said he couldn’t walk, the officer grabbed him by his ankles and dragged him to the car. It turned out the boy had been on crutches when he answered the door, and couldn’t walk.

Back at the department, I complained to the sergeant. I wanted to report the misconduct. But my manager squashed the whole thing and told me to get back to work.

I, too, have faced mortal danger. I’ve been shot at and attacked. But I know it’s almost always possible to defuse a situation.

Once, a sergeant and I got a call about someone wielding a weapon in an apartment. When we showed up, we found someone sitting on the bed with a very large butcher knife. Rather than storming him and screaming “put the knife down” like my colleagues would have done, we kept our distance. We talked to him, tried to calm him down.

It became clear to us that he was dealing with mental illness. So eventually, we convinced him to come to the hospital with us.

I’m certain many other officers in the department would have escalated the situation fast. They would have screamed at him, gotten close to him, threatened him. And then, any movement from him, even an effort to drop the knife, would have been treated as an excuse to shoot until their clips were empty.

* * *

I liked my job, and I was good at it.

But more and more, I felt like I couldn’t do the work I set out to do. I was participating in a profoundly corrupt criminal justice system. I could not, in good conscience, participate in a system that was so intentionally unfair and racist. So after five years on the job, I quit.

Since I left, I’ve thought a lot about how to change the system. I’ve worked on police abuse, racial justice and criminal justice reform at the Missouri ACLU and other organizations.

Unfortunately, I don’t think better training alone will reduce police brutality. My fellow officers and I took plenty of classes on racial sensitivity and on limiting the use of force.

The problem is that cops aren’t held accountable for their actions, and they know it. These officers violate rights with impunity. They know there’s a different criminal justice system for civilians and police.

Even when officers get caught, they know they’ll be investigated by their friends, and put on paid leave. My colleagues would laughingly refer to this as a free vacation. It isn’t a punishment. And excessive force is almost always deemed acceptable in our courts and among our grand juries. Prosecutors are tight with law enforcement, and share the same values and ideas.

We could start to change that by mandating that a special prosecutor be appointed to try excessive force cases. And we need more independent oversight, with teeth. I have little confidence in internal investigations.

The number of people in uniform who will knowingly and maliciously violate your human rights is huge. At the Ferguson protests, people are chanting, “The whole damn system is guilty as hell.” I agree, and we have a lot of work to do.