The grief of losing her daughter in a mass shooting at Montreal's Dawson College has weighed heavily on Louise De Sousa for nearly two decades.

As the 20th anniversary of the shooting approaches, De Sousa still finds herself wondering about the life her daughter Anastasia might have lived.

The what-ifs surface on ordinary days, but especially during family milestones, including births and weddings.

In a related development, “You always think back on that day and the what-ifs. Where would she have been in her life career-wise, married, children?” De Sousa wonders.

If she could speak to her daughter again, there are numerous things De Sousa says she would tell her. But she would ask one question:

"Why did you go to school that day, why didn't you skip?"

Furthermore, in her living room, surrounded by photographs of her loved ones, including some of Anastasia, De Sousa recalls the last morning she saw her daughter alive.

On Sept. 13, 2006, she went into her 18-year-old’s bubblegum-pink bedroom and asked if she wanted a ride to school, but Anastasia didn’t need one.

Later that day, a man would enter the school and open fire, killing Anastasia and injuring 19 people.

Additionally, de Sousa first learned about the shooting from coworkers while she was having lunch in her workplace cafeteria.

She and other family members tried calling Anastasia, but there was no answer.

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De Sousa went to the hospital after learning that injured people had been taken there. Hours passed and it was at 9 p.m. that she received confirmation that Anastasia had died.

“That night when we came home, I remember we were all crying. You could hear everybody crying in their bed and I'm waiting for the door to open to say: “Mom, I'm here,” De Sousa mentioned.

In the broader context, the days that followed her death were “a daze.” But thankfully, De Sousa had her family.

For her, moving through grief has meant going to therapy with her husband and supporting one another in the family.

Every year, De Sousa and her immediate family gather at the cemetery with Hayder Kadhim — a survivor of the Dawson shooting who was shot in the head — and his family.

Notably, for De Sousa, being surrounded by people who knew her daughter — and her granddaughters who never got to meet "Auntie Anastasia" — brings comfort.

They take a moment to stand together and talk to her; a ritual De Sousa carries into her home, too.

De Sousa says she talks to Anastasia every night.

Significantly, “There's not a day that goes by without her, without thinking of her or talking to her,” she noted.

“I can't fall asleep at night if I don't speak to her.”

And what she misses most is her daughter’s laugh.

Meanwhile, “She had this laughter that was so contagious. She would start laughing and, to tell a story, sometimes she never got through her story. But you were laughing now.”

Although Anastasia has been gone for nearly two decades, De Sousa says she still feels her presence around the house.

In the smell of her perfume – even when no one has sprayed it. In the bubblegum-pink strip of paint the family left in Anastasia’s room after repainting it. In the songs she used to listen to.

On a related note, “I hear songs from Sean Paul and all these old songs that she used to love back in the early 2000s and I see her singing it with her sister and her brother,” De Sousa mentioned.

Sometimes, she says, she sees shadows or hears someone call out “Mom” when she is alone in the house.

“I always tell myself: 'Oh OK, she's in here. She came.'”

In a related development, at times, De Sousa even places an extra plate on the table, absentmindedly, and leaves it there when she realizes what she’s done.

After her daughter’s death, De Sousa became an advocate with PolySeSouvient — a prominent Canadian gun-control advocacy group founded in 1989 following the École Polytechnique massacre in Montreal.

She believes the authorities should do more regarding gun control.

Furthermore, “Depending on the authorities we have, we do two steps back, one step forward, then you know, they stop. I find it should be a lot more severe,” she remarked.

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De Sousa also remains in contact with survivors of the shooting, some of whom she’s close to.

Additionally, “She passed away. But there's also 19 other victims that their lives, I'm sure, have been adjusted and not easy," she declared.

And De Sousa remains determined to ensure that the shooting — and Anastasia — are never forgotten.

“I want people to remember what happened. And I want those students to know what happened in their school. It's part of history,” she stated.

It is worth noting that “We’ve got to remember what happened. We’ve got to try and do better.”

Hénia Ould-Hammou is a Montreal journalist with CBC News. She previously completed an internship with La Presse after graduating from McGill University with a double primary in political science and psychology. Hénia is interested in international and societal issues, community stories, soccer, politics and rap. You can send her an email at henia.ould-hammou@cbc.ca

With files from CBC's Sean Henry