Sabaah Folayan was on a path to a career as a physician until life got in the way. And then she made an important documentary without knowing quite how to pull it off.

Opening Friday at the Lagoon in Minneapolis, “Whose Streets?” offers a sweeping account of racial strife and urban disarray.

“It was a huge learning experience,” she said during a recent visit to the Twin Cities. “It sent me off on an existential search for what I could do.”

When all eyes turned to the 2014 street protests in Ferguson, Mo., she felt called in a different direction. She saw the strife following the killing of unarmed black teenager Michael Brown by a white police officer as a story that needed to be told — not through context-free TV news helicopters, or outside reporters touring the working-class St. Louis suburb for a quick battlefield report, but from the perspective of the black community.

Making a record of the city’s grief and the individual lives affected became Folayan’s mission for the next year and a half.

“I felt like I had to go. I didn’t know what I was going to do or how I was going to do it,” she said.

Folayan, who grew up in South Central Los Angeles and now lives in Brooklyn, had scant practice in moviemaking and less knowledge of classic investigative nonfiction films. But she grew into the job fast. With a college friend in charge of still photography and Folayan writing, they posted their work on social media in hopes that followers would contribute enough to keep the project going.

“The way I wanted to rationalize it professionally was to say that I wanted evidence that there should be a public health study. The hypothesis was that people and police facing off every day was going to have a communitywide traumatic impact,” an idea that she still believes is true. Passing out printed surveys covering those questions in front of the Ferguson Police Department, “I immediately realized this was not the environment to conduct those kind of clinical interviews. That’s how we started filming. From the first interview we got, I knew it was clear that we had to keep following this story.”

St. Louis multimedia artist Damon Davis soon joined as co-director. Their research grew to over 400 hours of original footage, residents’ mobile phone videos of clashes and archival news coverage. Her intelligent, unsparing film, widely applauded in its debut at January’s Sundance Film Festival, whitewashes neither side in the conflict, showing civilians burning squad cars and looting stores while police officers lob tear gas and aim rifles at nonviolent protesters.

“We wanted a theatrical release, we wanted to go to Sundance, but the goal was always to tell a story that the people who lived through this experience could be proud of. The film industry success really came second to that. I always had faith that if we did it like that, whatever the product was would resonate far and wide.”

Three years after Brown’s death, “I don’t think the world has changed dramatically” in terms of prejudice, she said. “This backlash that we’re seeing now is what we see every time there’s a really progressive administration or upsurge in progressive ideals. You see the pushback of conservative ideals. I don’t think it’s anything particularly new, though it’s exacerbated by the tools we have [such as] the internet.

“Take the suspicion that a black person could be responsible for their own death, whether or not they’re armed, whether or not they’ve been a criminal, whatever the laws are. There’s always a suspicion that when there’s a black person involved, there could possibly, probably, be a reason why they deserved to die. And that is deeply, deeply rooted in the American psyche. That’s why it’s difficult for reformers to push back on that, because you’re dealing with really subconscious, implicit ideas” still coming to light.

Folayan says that the Black Lives Matter movement, founded after Brown’s death, has already been a corrective influence.

“It’s absolutely making a difference because it’s drawn a line in the sand. I don’t know any organizers who are proposing to have all the answers. A lot of us are young, just new to the professional world or having children and just starting our lives, understanding our place in society. But we’re asking the question, putting the question forward, forcing people who do have the expertise and responsibility to respond to it. That is what our job is as citizens.”