“Black lives are too easy to take in America because we don’t want to question why people are so afraid of black and brown people to begin with,” says Yance Ford, bluntly. “And that’s what I want Strong Island to do.”

When Ford began making his documentary, 10 years ago, this was not a question that the US was particularly interested in asking itself. In the intervening years, following a succession of slayings of innocent and unarmed African Americans, it has become part of a national conversation – although it is turning into more of a national argument. What began for Ford as an intimate, personal film now finds itself part of that argument.

“When I started this, it was: ‘I have to get this burden off my chest,’” he says. “Then, in 2012, when Trayvon Martin was shot, everyone came out of the woodwork like: ‘Your story’s so relevant! So relevant!’ I saw the word ‘relevant’ in my Facebook feed, like, a million times that year. Then I jumped off social media, but I wasn’t able to turn off the world. It kept happening and happening.”

William Ford Jr with sister Lauren (front left) and Yance (front right). Photograph: Netflix

Ford’s documentary focuses tightly on the taking of a single life: that of his elder brother. One night in April 1992, William Ford Jr, a 24-year-old African American, was shot dead by Mark Reilly, a young white mechanic. Ford was unarmed. He had gone to Reilly’s Long Island auto-repair shop to pick up his car. They got into an argument. There were no witnesses to the shooting itself, although there were plenty of people around, including Ford’s friend Kevin Myers. When the police showed up, they treated Myers, and the dying Ford, like criminals, rather than victims. The shooter, meanwhile, was discreetly spirited away from the crime scene.

“Just wait till we get to court,” said Ford’s mother as they buried William. But the case never went to court: an all-white grand jury decided, behind closed doors, that there was no basis to indict the shooter. It was a simple case of self-defence and “reasonable fear”. That’s just about all the Ford family were told. The case file remains sealed.

Strong Island is not an investigative documentary. Ford’s attempts to speak to those involved with the case are rebuffed. Questions about official procedure, conduct and extra-judicial influence go unanswered. The film is more an anatomy of an injustice – one that many African American families will recognise.

Ford registers the slow, devastating impact of the incident on his family. Their father died after a stroke within a year of William’s death. His mother, Barbara, speaks eloquently and movingly of her loss, and the silence that fell over the grieving household. She died in 2012, during the production of the film. Ford believes that 20 years of “stress and self-blame and second-guessing and disappointment and anger” contributed to her death.

Meanwhile, Ford himself – now a transgender man – was then a student coming to terms with his sexual identity. “I pivoted from going to the counselling centre to figure out how I was going to come out [as a lesbian] to my family to going to the counselling centre to figure out how I was going to deal with my brother being murdered.”

What makes Strong Island stand out – and what earned it awards at Sundance, Sheffield and other film festivals – is its combination of universal resonance and personal authorship. In the former instance, it is an emblematic tale of shattered faith in the American dream. We learn how the Ford family moved north to escape the ingrained discrimination of the south, where Ford’s grandfather died of an asthma attack in a “coloureds only” doctor’s waiting room, yards away from medical help. We learn how Long Island’s racism was better concealed – how black families were permitted to buy property only in a few tightly zoned areas. His parents became public-sector workers: his father worked on the trains; his mother taught female inmates at New York’s Rikers Island prison. William was also a teacher, and was training to become a corrections officer when he was shot. These were people who believed that American society would provide for them if they played by the rules.

Yance’s mother, Barbara Dunmore Ford, circa 1958. Photograph: Yanceville Films/Netflix

“She expected it to work out,” Ford says of his mother. “But we’ve seen that, however strongly you buy into the American dream, however many of the rules of blackness that America draws for you you follow, no matter what you do, who you are, where you are, you are not safe, and that’s quite a heavy thing to realise,” says Ford.

In the latter case, Strong Island avoids standard documentary techniques and establishes its own unique aesthetic. Ford trained as an artist and architectural welder, and worked as a documentary series editor before and during the film’s long production period. He has clearly had time to think about it. The story is punctuated with carefully composed tableaux that express the unsayable: a blind, flapping in an empty room; a time-lapse cloud bursting over the family home. And in several striking scenes, Ford addresses the camera directly and frankly, his shaved head looming out of a black background and filling the frame. “I’m not angry,” he says to the viewer at one point. “I’m also not willing to accept that someone else gets to say who William was. And if you’re uncomfortable with me asking these questions, you should probably get up and go.” It is an arresting device, both confrontational and confessional.

“I had a list of 10 rules when we started Strong Island, and one of them was: ‘Yance will never appear on camera with sync sound,’” Ford laughs. “I sort of did that director’s trick of: ‘Let’s just shoot it anyway, even if we’re never going to use it.’” He was being interviewed by other film-makers for those scenes, he explains. Just like his own subjects, he didn’t know what questions he was going to be asked. His responses surprised him: “I was saying things out loud that I had never said before.”

At one point, for example, Ford talks about how he has never wanted to see an image of his brother’s killer. As a result, he says: “I think he looks like, no offence to present company, every white man I’ve ever seen … he looks like anybody, anyone, everyone. He’s everywhere.”

It’s a bold admission. Did he think twice about putting it in? “No, because it’s true. What black people are almost always called upon to do, and we saw this with the Charleston shootings [in which nine churchgoers were killed by a white-supremacist in 2015], is to forgive and offer redemption. I have no interest in forgiving anybody. I have no interest in telling a redemption story. I have no interest in giving Mark Reilly any space in this film. When you shoot my brother, you’ve said everything to me that you have to say.”

But is there a danger that characterising all white people as potential killers is mirroring the racism he is calling out? Isn’t such “othering” only strengthening the racial divide?

“I’ll tell you why I don’t think it is,” he says. “White communities, and I exempt poor white communities from this, have power over their representation. White people have the ability to define themselves, to exert their agency in a way that they get to be believed. No one believes black people. No one. Until a white person vouches for them. That’s what so many of these murders have in common: ‘Strong, scary, big, black, angry, out-of-control’. How many times are we going to have to hear that about a black person? So I reject that it’s an othering.”

It is no cause for celebration that the “relevance” of Strong Island, and other films presenting the African American experience, continues to grow. The first time I spoke with Ford, it was already clear that the Trump administration was set on rolling back Obama-era reforms to the criminal justice system. In July, attorney general Jeff Sessions, for example, announced plans to reinstate mandatory minimum sentences for minor drugs offences such as marijuana possession, which have disproportionately affected black and Latino citizens. Since then, we have had President Trump’s pardoning of sheriff Joe Arpaio, not to mention heavily armed Nazis, Klansmen and white supremacists marching through Charlottesville, a grotesque spectacle compounded by Trump’s failure to condemn them.

Strong Island, available on Netflix from 15 September. Photograph: Yanceville Films/Netflix

“The imagery is straight out of the south from which my parents fled,” says Ford when we speak again. “They could have been marching towards a cross to set it on fire.” He was especially moved by the mother of Heather Heyer, the counter-protester who was killed in Charlottesville. Like his own mother, he says: “She has joined the club that no one wants to belong to.” “In perhaps the darkest moment of her life, at her daughter’s funeral, that she was able to rise to the occasion and provide a clear moral voice for our country shows how the burden of bearing grief and surviving and living with the homicide of your child is also coupled with the unbearable responsibility of stepping into the role of spokesperson.”

As for the presidential pardoning of sheriff Arpaio, Ford notes that it is “a de facto admission of guilt. To use such a powerful tool to essentially undermine the courts to support a man who has been judged, after years of investigation, to be wilfully violating human rights, engaging in racial profiling, who was voted out of office by his district, but who still doesn’t think he’s done anything wrong. It’s horrifying.” These incidents do, at least, provide incontrovertible proof of the racism in US society whose existence Ford and so many other African American families have asserted for decades. In the past, it was denied; now it is acknowledged and accommodated, which is even worse.

I am reminded of the quote attributed to Martin Luther King, which President Obama had embroidered into a rug in the White House: “The arc of the moral universe is long, but it bends towards justice.” In the Obama era, it felt as if that was starting to happen; now, less so.

“Now it’s more: ‘Will it or won’t it?’” Ford agrees. The counter-narrative is already pushing back, he says. He expects to be in the line of fire himself when Strong Island is released. “And I will push right back against it,” he says. “Because I can do now in 2017 what my family was unable to do in 1992, and I am bound and determined for that arc to bend towards justice for my family.”

What has become starkly clear is that it doesn’t just bend itself.

“Some people gotta bend it!” he says with a smile. “You know, I’m a welder. I know how to bend things. You just need a little bit of heat over a long period of time.”

Strong Island is on Netflix from 15 September