After my sister killed her abusive partner, I raised their 2 children. I've learned a lot about sistering and mothering.

• Michelle Horton's sister, Nikki Addimando, served more than six years in prison.
• Michelle raised her niece and nephew, as well as her son.

This as-told-to essay is based on a conversation with Michelle Horton, author of "Dear Sister: A Memoir of Secrets, Survival, and Unbreakable Bonds." It has been edited for length and clarity.

In September 2017, the police knocked on my door with a very cryptic message. My sister, Nikki Addimando, was at the police station. I needed to pick up my nephew Ben, who was 4, and his sister Faye, who was 2.

Over the course of the day I learned that my sister had shot and killed her partner, the father of her children, a person I had known for a decade. It was the craziest thing that someone could have told me about my nurturing, maternal sister. Eventually, I would learn that her partner, Chris Grover, was horrifically abusive, and she killed him to save her own life.

At that moment, I only knew we were a family in crisis. I had recently become a single mom after ending my marriage. Now, I would be caring for two highly traumatized children, plus my own son, Noah, who was 8. Nikki was facing possible life in prison, so I was also spearheading the effort to get her legal support.

I was determined to face the ugly truth

Early on, I realized that one of the most loving things we can do for our family is to be truthful and honest. That hadn't been the case for the family that Nikki and I grew up in. Our family had a culture of denial and sweeping things under the rug. If we weren't talking about it, it wasn't happening. Our parents took this approach even with life-changing events like Nikki's childhood sexual assault.

Even before the police knocked on my door, I was done with that. I was committed to facing the truth, no matter how ugly it was.

Of course, I never could have imagined the truth that landed in my lap. And yet, I didn't shy away from it, even when Noah asked me why Nikki wasn't around, and even when I had to explain to Ben, and later Faye, that their mom was away because she had killed their dad.

Trauma-informed parenting made me a better mom

Before Ben and Faye ever came to my house, they'd survived domestic violence. Now, they were facing the primal trauma of being separated from their mom. I learned a lot about how trauma impacts the body. Some days, there was no way Ben could go to preschool. Instead, we would go for a run so he could calm his body and have an outlet for everything his body was feeling.

One of the most radical changes I made was validating and mirroring back the kids' feelings. It's easy to tell kids things are fine and they are safe. To really sit with their pain is much more difficult. When Ben said he'd lost everything, I told him he was right. When Noah talked about the loss of being an only child, I acknowledged that our family was different from what either of us had pictured. Becoming a trauma-informed parent made me a better mom to Noah.

Nikki is home, but my work isn't done

Nikki was initially sentenced to 19 years to life in prison — a sentence that her children and I would have served alongside her. A year later, her sentence was reduced to 7.5 years under The Domestic Violence Survivors' Justice Act. In January, Nikki finally came home.

Right now, we're all so happy together. Nikki moved in with the kids and me so we can enjoy the incredible gift of everyday moments like being able to eat or sleep together. We all marvel that we are finally home together.

Writing my memoir was part of my healing process. The kids will continue to heal throughout their lives. Now that Nikki is free, she can start healing from the abuse she endured, which was compounded by the legal and prison systems.

People tell me our story is unimaginable. But I was them to imagine it and feel the raw emotional impact. There are women and children in danger in every community. There are thousands of kids in foster care, processing the trauma of their parents being incarcerated survivors of domestic violence. I've learned we can't look away.