Lee Lawrence, 46, won the Costa biography award this month for his memoir, The Louder I Will Sing. It documents the shooting of his mother, Cherry Groce, in 1985, by police who forced their way into her home. Lawrence was 11 at the time and in the same room as her when she was shot; the police were looking for his older brother who didn’t live there. The book also covers the uprising in Brixton that followed, his mother’s subsequent paralysis, her life afterwards and early death, as well as her son’s mission to tell her story. Lawrence sits on police advisory boards in Brixton and is founder of Mobility Taxis, a social enterprise providing wheelchair-accessible transport, and a charity in his mother’s memory, the Cherry Groce Foundation.

How did it feel to win the Costa biography award with your first book?
It was fantastic, but I was taken aback. I didn’t write my book to be accepted as a writer. I wrote it because of a mission to tell a story that felt important to tell, in a way that would connect with people and bridge an understanding between their lives and ours.

What did you want the book to do?
I wanted people to read the story of what happened to us as a family and think about unconscious bias, then about the people they live near or work with, think what can we learn from this together, then reach out. Yesterday, a police officer got in touch to say he’d read the book and was touched to tears. He wanted to connect with me somehow. That’s how I measure the book’s success.

You first tackled your mother’s story with your aunt, actor Lorna Gayle, in a short play, Her Story, staged at Brixton’s Ritzy theatre in October 2011. That was only seven months after your mother’s death. How was that experience?
It was a creative collaboration done between us, very quickly, depicting where we were [they had discovered Groce’s death had been as a result of an infection ultimately caused by the shrapnel in her spine; it took three years for an inquest to prove that multiple shocking examples of “police failure” contributed to her death]. That’s when I really started piecing together what happened to my mother as an adult. Remember, I was only a child at the time. I went through paperwork my mum had kept from the initial inquest and began unloading everything in my head on to paper. It felt like writing a diary of the past.

Was that cathartic, traumatic or both?
It could be very emotionally draining, like going to therapy sessions. Sometimes, it would take me a day or two to get back some balance again.

You have dyslexia and wrote a lot of the book by dictating its lyrical passages into a dictaphone. How was that process?
It addressed my number one concern: that this book had to be authentic. I wanted people who knew me to read it and say, yes, that’s the way Lee’s language flows, how he speaks. I loved revisiting the parts of my childhood before the shooting. There was so much joy, laughter and excitement in our lives. The structure [moving between sections entitled Before and After, exploring life before and after his mother’s death], was a collaboration with my editor. That helped me connect the present and the past.

Language is clearly hugely important to you. You talk about how the events after your mother was shot in Brixton are still referred to as “riots”, not an uprising, and how Inspector Douglas Lovelock said at the inquest he was “disappointed” that this happened when referring to having shot your mother.
I’ve always known that the way an idea is phrased or expressed can offer such a different idea of what it is. What happened to my mum was drowned in the language of “riots” and “thugs” on the news. A woman was shot in her house early one morning in front of her children. There was an uprising as a result of the hurt and pain caused by that action. That was the [real] story.

The need for racial diversity in publishing has been pressing in the last year. What have your experiences of the industry been like?
Most people I know who have published books have self-published. I always thought that was my only road, so I hope my book being published by a mainstream publisher gives encouragement to others. My project was signed up in 2019, long before the Black Lives Matter protests, and I do worry that people might see some projects being about publishers jumping on a bandwagon. That support needs to be consistent and we mustn’t be complacent. We can’t have a year where there’s a flurry of black voices and then nothing. The same goes for good film-makers, actors and directors.

What books are touchstones in your life?
I came to reading late and audiobooks changed my world. [Susan Jeffers’s] Feel the Fear and Do It Anyway helped me put courage before fear in my life. [Eckhart Tolle’s] The Power of Now also helped me manage my past and my expectations of the future. During the inquest after my mother’s death, it made me focus on being present in the moment, realising the rest is out of your hands. Akala’s Natives is a recent book I’ve loved. He has an ability to understand, convey and articulate big ideas and be respected. He’s really making a difference.

Is another book in the pipeline?
I keep thinking if I’ve been able to come through what I’ve come through, and convey this story in the way I’ve conveyed it, and it’s connecting with people, what else could I possibly do to create more balance in the world or help make a fairer society? Things are coming to me that I feel could further open people’s minds and that could possibly be through another book. Anything I do, though, will be in that vein.

• The Louder I Will Sing by Lee Lawrence is published by Sphere (£8.99). To order a copy go to guardianbookshop.com. Delivery charges may apply