Twenty children and six staff members were killed in Newtown, Connecticut, on December 14, 2012.
It was the deadliest mass shooting at an elementary school in US history.
The 20-year-old gunman also killed his mother that day and shot himself after the massacre.
On December 14, 2012, a 20-year-old man walked into Sandy Hook Elementary School in Newtown, Connecticut, and shot 26 people, including 20 children, after also killing his mother in their home.
News of the massacre reverberated across the country and elicited a tearful reaction from then-President Barack Obama, who described it as the worst day of his presidency.
Sen. Chris Murphy, who had previously been a representative for the district that included Newtown, was among those present when the families of the victims learned about the fates of their loved ones.
"'I'm so, so sad today," he tweeted on the sixth anniversary in 2018. "Sad for the searing loss, that hurts like hell every Dec 14th for those parents, my friends. And sad that I sent my youngest off to 1st grade this morning, and that I work with people who care more about politics than making sure he comes home safe."
In the decade that has passed since that day, many of the parents and families launched foundations in their children's names to help others, and become advocates for gun control.
And in early August, conspiracy theorist and Infowars founder Alex Jones was ordered to pay $45.2 million in punitive damages to two parents whose son was killed in the Sandy Hook massacre in a defamation trial after he spent years calling the shooting a "hoax" and the victims "crisis actors." Neil Heslin and Scarlett Lewis, the parents of six-year-old victim Jesse Lewis, were also awarded $4.1 million in compensatory damages in the defamation trial against Jones.
Jessica Rekos, 6, told her mom, Krista Rekos, that morning before she got on the bus how excited she was to sell Girl Scout cookies that January. "She sat in the front seat, looked at me through the window, and smiled and waved as the bus pulled up the hill," Krista wrote. "That was the last time I saw Jessica alive."
Avielle Richman, 6, "was rarely without a giant grin and often barefoot." Her family founded the Avielle Foundation "to fund research exploring the underpinnings of the brain that lead to violent behaviors."
Caroline Previdi, 6. Her family founded a foundation in her name to give kids scholarships to support their passions. "When talking about our family, or herself," they wrote, "she would tell people, 'We are not lucky. We are blessed!"
Allison Wyatt, 6, wanted to be an artist, and rows of pictures filled her house. Her parents wrote that they found picture Allie had drawn for her first grade teacher, Miss Soto. It read: "I love you, Love Allie".
Victoria Soto, 27, died while trying to protect her students. Soto put her students in a closet and "by doing that put herself between the gunman and the children," Soto's cousin told ABC News.
Mary Sherlach, 56, was the school psychologist. She was only one year away from retirement, after which she and her husband planned to spend time in their cabin along upstate New York's Finger Lakes, according to Newtown Patch.
Rachel Davino, 29, barricaded the classroom to try and keep the gunman from getting to the children. Her boyfriend had asker her parents' permission to marry her days before the shooting. He was planning to pop the question on Christmas Eve.
Anne Marie Murphy, 52, was a para professional at the school who worked with a boy with special needs named Dylan Hockley. Her body was found covering a group of children, and she died with Dylan in her arms.