Since his transition from football running back to actor, John David Washington has starred in films that tackle social issues. His latest, Spike Lee’s “BlacKkKlansman,” continues the trend as Washington plays real-life police officer Ron Stallworth who became the head of a Ku Klux Klan chapter. When Lee first called, the “Ballers” star says he couldn’t believe the story was true.

How did you research the role?

Between all the internet searching and interviews, I was asking Spike if I could talk to [Ron Stallworth], if I could contact him and he wouldn’t let me yet. He was like, “Not yet.” I thought that was brilliant. The fact that he didn’t want me to do it too far out. He wanted me to have contact with him closer to principle photography. So I was just finding stuff on the internet, reading up on him, rereading the book, and [doing] extensive note taking. When the rehearsal process started to happen, and this was September, he came to the table reading, Ron himself. I talked to him and we kept in touch the entire time while filming. It was great. He was so generous with his information and what he was going through emotionally, spiritually, all of that throughout the entire case. What motivated him to want to serve his community. Again he was very open and candid with everything that was going on in the ‘70s. It was a crazy time. The fact that we was able to pull this off during those times—I can’t believe it. It’s crazy. It was a great process to have him onboard. It really helped me so much during the process and finding truth in this character, with Spike Lee telling the story [and] all the information he was able to give me.

Was there a key piece of advice or story that Ron shared with you?

There were several pieces, some that I cannot share. It’s between he and I just because of how personal it is. What I will share is the fact that he was, and I think it’s in the film too, the Jackie Robinson of police officers in Colorado Springs. There was a lot of pride that went into that—that he was the first African-American to be a detective, to be in the police force in Colorado Springs. What that really means in the ‘70s—he was able to give me great insight on that, some of the pressure. He kept saying it always about the job. He never got emotional, even with the specific case the film is based off of, the book is based off of. He never made it personal. I didn’t believe him to be honest. I was like, “C’mon man. There’s too much at stake and given the social climate of where the country was then—it’s crazy where it is now—you had to have some emotion.” [Then] I was getting into it and starting to understand and breaking these stories down. I don’t think he could have been emotional and been able to pull this off. I think he really had to keep the mandate at the forefront which was no terrorist activity or violent acts during the investigation and trying to take this organization down. It was all about the law for him.

Were you able separate from the material when filming stopped?

Yes and on so many different levels no. When you hear the voice of your director, when he says, “Action,” it’s one thing—you activate, you go into the character. But it was Spike Lee yelling this to me! On set! That was great! And yelling “Cut!” on set. I’m on a Spike Lee set. So every day I’m like, “I can’t believe this!” I’m getting joked up right now even thinking about it. “I can’t believe I’m in this environment, my childhood hero.” For years, all these films, just growing up watching, idolizing the types of performances he’s been able to get out of actor, these performers we’ve loved and grown up loving, at least ones that look like me. That was so surreal. Trying to separate the emotions of that was tough. I really got into [the character]. But I was able to let it go at the end of days. But sleepless nights. I wasn’t sleeping a lot because I was always thinking about the next day. But, it was such an ease on set. I never felt a more collaborative environment ever. Spike Lee [and Stallworth] really trusted me. They really trusted me [with] giving his point of view and telling the truth of this man and the story. That was such a freeing experience—knowing that your captain, a captain you’ve loved and admired your entire life, trusts you with this kind of information, with this piece. It was encouraging and it was freeing to just be able to make all kinds of choices as an actor.

Was there a specific direction Lee gave you that helped during film?

I guess this could be a bit anticlimactic but he told me one time and I quote, “Put some bass in your voice.” We had been shooting a week already. It was a lot of physical movement. It really wasn’t dialogue we were doing. It was ad lib stuff. It was a week later and this is the first time I’m saying stuff that’s on the page. So, emotions are running high a little bit. It’s Spike Lee and all that and I’m hyped up. I’ve been studying and having this guy’s spirit for months now. Here we go. A couple takes we do it—it’s all good. He comes up to me. He’s not looking at me. He just comes up to me. He’s looking away. He gives me a couple technical things. Still looking away, not looking at me, acting like he’s thinking about something. He says, “Put some bass in your voice.” [Laughs] At first, I was embarrassed and I started busting out laughing. But for some reason, it charged me up. Those words blew confidence in myself and I was just able to go out there and handle business. Those words just activated something that I guess I needed to hear.

What conversations do you hope the film generates?

To hopefully just do that. We can start a dialogue to recognize the differences in opinion and maybe learn what we don’t know about each other. Once we can find out what we don’t know, that’s when we come into information and maybe something we find out can break the barrier, the wall. Start communicating and find out how we can relate. Hopefully this can be an opportunity to recognize how reactionary of a people we are. We are emotionally driven—you hit me, I hit you. Maybe if we can kind of reverse the motive and try to have a new approach to the recognition of our differences and find some common ground.

Watching the movie—it is a period piece but conversations in this sound very familiar. They feel very contemporary. Not in the style of the film but just the actual subject matter. This is happening right now, still. The film doesn’t suggest or try to nudge you to choosing a side. It’s just laying out how people feel, how divided this country is. I think this certain kind of organized hate is instituted. It’s taught. So maybe seeing that, exposing some of that, maybe we can find a way to install dialogue and start the dialogue.

You are also starring in “Monsters and Men.”

Reinaldo Marcus Green—I’m so blessed an honored to have worked with him. We went through Sundance labs together. I’m so excited about the process that we took our time with it to get this done. It started with Sundance labs—just a lot of dialogue. We took our time. He didn’t skip any steps. The filming had a tight window but the preparation—it wasn’t cheapened. When you see the final product—that’s what I got emotional about. The seeds grew into beautiful plants. Hopefully people connect to it.

How do you choose your projects?

It was just meant to be. It happened organically. It was Skype with Reinaldo, a phone call with Spike Lee. I had to fight more for Reinaldo. That was more of an audition process. These are the kind of films I want to do—impactful films. All different kinds of genres, not just comedy not just drama, but life. Being able to tell people’s stories—this is the most exciting job in the world to me. We’re in such a privileged position to be able to tell stories of people in this country, all over the world, what they go through. When they come to the theater on a Friday night they can forget about all their troubles and worries for a couple hours and just get lost in these characters as I did and still do. Movies are magical. It transcends a lot of hate or human faults in real life because of the fantasy of it all.

What have you learned about police officers after playing one multiple times?

Extremely stressful job. Maybe that might be common knowledge but it’s a very underappreciated job. It takes a toll on you physically. I think there are some men and women out there that are serving our community, really doing their job. They are really making a difference and changing at least one or two kids and that could spark future leaders that can lead the country into a new way of thinking. A more inclusive country. It is a tough job. The hours alone can be very stressful. Putting their lives on the line every day. They might not be able to see their families again. It can happen at any time and they still [have] to go out there and do it. You have to love your community. The men and women that are doing it the right way are there to serve their community. That’s a hell of a commitment every day for almost a thankless job.

“BlacKkKlansman” premieres at Cannes Film Festival on May 14.