A young black man, shot. A family in mourning and a justice system scrutinized. This isn’t the story of slain teen Trayvon Martin – although it sounds uncannily similar – but of Oscar Grant, a black 22-year-old who was shot by a police officer in 2009 after being detained at the Fruitvale Station stop as he was returning to his San-Francisco-area home after celebrating New Year’s Eve.

“If we could stop this from happening, we could end so much pain,” says actress Melonie Diaz, who plays Grant’s Mexican girlfriend Sophina in “Fruitvale Station,” a new film based on Grant’s (played by newcomer Michael B. Jordan) last hours and death by a police officer’s gun. “Latinos and African-Americans know this pain equally,” says Diaz, “and I feel Sophina and the family that were left behind are victims as much as Oscar was.”

Diaz met the real-life Sophina and the daughter she shares with Grant’s only daughter in preparation for her role in the film – currently playing in select cities – by first-time writer and director Ryan Coogler. And Diaz – who grew up “fairly poor” in what she describes as the “projects” in New York City’s Lower East Side neighborhood – says that her one-on-one time with the family strengthened her resolve to break down barriers regarding race both in Hollywood and beyond.

“I’m familiar with life’s struggles,” says Diaz, who first became interested in acting as a student at NYC’s Professional Performing Arts High School. “Sophina said Oscar was a great father – I heard that straight from her. Despite his infidelity, despite his past mistakes, he was a family person and she had a lot of unconditional love for him. She was extremely strong and that’s what I wanted to bring to my performance. There’s a side to him and the entire family that I think was missed when the accident first occurred.”

As the only actress in her Puerto Rican family, Diaz says her role in “Fruitvale Station” – which won the Grand Jury Prize and Audience Award at the 2013 Sundance Film Festival – exemplifies why she has dedicated her life to telling stories about character, strength and determination through film.

“I’ve been doing smaller movies because I really want to do things that are unique and say something,” explains Diaz, who has appeared in indie films like last year’s “Supporting Characters” and 2002 classic “Raising Victor Vargas.” “My focus is on longevity. I don’t want to do things that are complacent; I want to be in things that are weird and test people’s emotions.”

And as it turns out, Diaz earned more than a paycheck during the time she spent filming “Fruitvale Station,” which will be released nationwide July 26. The 29-year-old – whose list of forthcoming on-air roles includes a guest spot on the upcoming season of HBO’s “Girls” – says she found a kindred spirit and mentor in “Fruitvale Station” co-star Octavia Spencer.

“I learned from her that you can be super successful and still be really nice,” shares Diaz of Spencer, who earned an Academy Award for her role in 2011’s “The Help.” “She’s so giving and a ray of sunshine. She’s really become a mentor for me throughout this process. We talked about being women of color because you know, it’s great you know, to be bronze kin.”

Diaz says that Spencer even returned her “Fruitvale Station” salary when she learned of the budget constraints on set; a decision, Diaz explains, that taught her something “really valuable.”

“She gave it [her salary] back and I think that says a lot about a person’s character when you believe in something so much and give it all up for the sake of a project,” says Diaz. “She told me to be strong and fight for what you think is yours. And that sometimes, being persistent really pays off.”

And it’s a lesson that Diaz says she hopes to put into practice. She may be known as an indie film actress, but she’s ready to go mainstream.

“I’m not above that,” explains Diaz. “But sometimes I feel like they’re not ready for me. I want to be interesting, unique and say something that really matters.”