Transcript for 'Black and Blue': Black police officers navigate a divided country
This is my own neighborhood. When she walks these familiar streets, it's like she never left. You literally know everybody. I used to walk the beat. As she strolls through this San Francisco neighborhood where many view police as a foe, most everyone sees her as a friend. Don't get scared. Across the country in Pittsburgh, it is the same for officer Andre Wright. They used to call the former college athlete dre the athlete. Now he's he dre the cop. But not much has changed. They're my people. It is what it is. At a time when tensions between police and black communities are explosively high, the divide between Americans can feel irreparably deep. Caught in the middle of a precarious balance. As one officer put it too, black for the badge too, blue for the hood. In our series, collaboration with the partners of the undefeated. There's a blue lives matter and a black lives matter in this country. Where do you fall in that? Well, you know, I have told people that I am always going to be black. But I'm only blue as long as I continue to wear the uniform. She joined the force nearly 30 years ago as part of the justice department's push for diversity in SFPD's ranks. She was an unlikely candidate then. I was complaining with the blat an drug deals. I complained about the police cars that just drove by the area like they didn't even exist. These police officers said stop complaining. Get in the game. Right. So you became an officer. Yes, against my better judgment, I became a police officer. I mean, the police officers in my concept, they're so manly. Back in her early days, walking the beat chronicled by KGO, she was hopeful. Idealistic. I feel like this is my ultimate calling and I love it. I thought just one big happy family until 2015. I found out that there were some who just didn't feel the same connection. Two years ago, one of her colleagues had been convicted of fraud. During his appeal, investigators stumbled upon racist and sexists texts between him and other cops. Shock goly they singled out one sergeant-year-old Andy a Williams. I said get out of here. You didn't want to believe it. I didn't want to believe it. So what messages stick out in your mind? I was someone's black -- It refers to them as savages and animals. An undeniable police bias and discrimination. Justice should occur in this situation. In January, 2016, she toefd a blue ribbon panel there was bias in the ranks. Rather than defend Yolanda, they rebuked her writing in a public letter that her testimony was largely self-centered and grossly unfair. Soon after, she left the police union. The union responded by saying, we are certain that the vast majority of our members, including officers of color, do not agree with her either. We are committed to diversity in our ranks. But the department of justice had been investigating SFPD and in October 2016, it strongly recommended nearly 300 institutional changes, identifying implicit and institutionalized bias against minority groups. That fall she was promoted along with 18 other black officers. These days, lieutenant Yolanda Williams is the president of another union. There is no time to sit back and bask in the sun and say we made our accomplishments and we'regood. She identifies with the trust and even fear many have toward the police. When you're not in uniform and you see blue lights behind you, you get pulled over. My heart stops and I all of a sudden find myself in a situation of, what did I do? Keep my hands at the steering wheel. Don't move. I don't have that reaction when I get pulled over by a police officer. You don't? Huh-uh. Wow. Doesn't that tell you something about where we are? Something wrong. Majorly wrong. Historically, the policing institution arose from out of slave catchers. So he that is the foundation of the institution alibi as that's exist within the police department. A black young cop, it's like the uniform. For officer Andre Wright, with just five years on the force, the problem isn't the system. I don't agree with institution alibi as, per se. I believe there are so many individual personalities, when it comes down to being a human and cops are human. He said the best way to right the wrongs is with officers like him. I'm supposed to be in the neighborhood but I have such a personality, I guess, they allowed me to deal with certain incidents and certain things across the city. He comes from a troubled past. I've seen people shot. I've had a gun pulled on me. There's a lot of bloodshed, a lot of guys who didn't make it. A lot of the guys I grew up with didn't make it. It's sad. Even people my age, they're like, you were crazy in high school so it gives me hopeful. His current job is a bit undefined. Like Yolanda, you can find him at a football game, at the park, walking the streets. Anywhere he gets to interact with people. I ride around and I basically got anybody that needs some help or, I believe I can insert myself into a position in life, I try to. Like an ambassador? I would say just a good cop. A former college football star at Pitt. He stumbled into a police internship. He remembers helping a woman recover a wallet. She was very grateful for what we had done. I like this. I can do this. Like San Francisco and 69 others in the past 20 years, the spurring police was also investigated by the justice department in 1997. In spurring, thpittsburgh, they found racially insensitive language against African-Americans. I recall the old days. But rather than blaming the system, he challenges others to be part of system. I don't see anyone I know. I don't see a cop that I recognized. Why would you not become an officer? He does whatever he can to keep things from escalating. There's not much that you can say to me that I haven't experienced. 40-year-old female, threatening suicide -- So this is a suicidal female. So we're at the site. She's threatening suicide. We'll check it out. She was depressed about her boyfriend leaving. She wasn't trying to hurt herself. My job is 85% social work and probably the rest, 15% police work. And lots of charm. Thank you for everything you did, for making our streets safe. Like more than 70% of officers, he's never had to use his weapon on duty and he wants to keep that it way. We have nightmares, having to shoot somebody. It's scary. That fear is something he wishes his community understood. We get afraid. As many times as you make a mistake, my mistake will cost a life or my job. With tensions high, both are pleading for mutual understanding. How do you explain blue lives matter to the rest of the world? It's not to say that police officers matter anymore. All we're asking for is for you to be a little bit respectful for the fact that we're putting our lives on the line. It's nice to meet you. Respect and compassion, an ethos they both share. To have the servant's attitude. If you can't be a servant, this is not the correct career for you. I'll give him a @little update. You just fill him in. All right. Thank you. Life is short. I make a difference in somebody's life. Even if I affect one person in my whole life, I'm all right with that. I'll rest in peace. For "Nightline." Our story tonight was done in collaboration with our friends at ESPN and the undefeated. To learn more about these officers and others featured in their special report, please go to the undefeated.com. Coming up next, a bear
This transcript has been automatically generated and may not be 100% accurate.