Erica Lafferty lost her mother on Dec. 14, 2012.

The late Dawn Lafferty Hochsprung, then principal of Sandy Hook Elementary, was killed when 20-year-old Adam Lanza stormed into the building and fatally shot 20 children and six staff members, before shooting himself in the head.

That was days after the final Thanksgiving she and her daughter would share.

As Lafferty wrote in USA Today on Friday, “This Thanksgiving, I sat at a dinner table with an empty seat. It’s the very seat where my mother, Dawn Lafferty Hochsprung, should be. Smiling, laughing and enjoying a holiday meal with her daughters and grandchildren. . . . My heart – and my dinner table – reflect the hole in my life that will never be repaired.”

Painful as the experience has been, it led Lafferty to her current calling as an advocate for gun safety.

It must feel like salt in an open wound, then, when someone denies that the Sandy Hook massacre ever happened in the first place. But that’s exactly what conspiracy theorist Alex Jones, a Donald Trump booster and founder of Infowars, has claimed repeatedly. See for yourself.

As reported in the New Yorker:

“Jones’s amazing reputation arises mainly from his high-volume insistence that national tragedies such as the September 11th terror attacks, the Oklahoma City bombing, the Sandy Hook elementary-school shooting, and the Boston Marathon bombing were all inside jobs, “false flag” ops secretly perpetrated by the government to increase its tyrannical power (and, in some cases, seize guns). Jones believes that no one was actually hurt at Sandy Hook – those were actors – and that the Apollo 11 moon-landing footage was faked.”

Trump is a Jones admirer. Trump once told him: “Your reputation is amazing. I will not let you down.”

After Trump became the president-elect, he continued to be lauded by Jones, and Trump hasn’t spoken a word against the conspiracy theorist. Instead, Jones claimed Trump promised to appear on his show again, The Washington Post reported. And Trump continues to quote baseless claims from Jones’s Infowars about millions of Hillary Clinton supporters voting illegally.

Lafferty could no longer hold her tongue, as she wrote in a long op-ed for USA Today that published on Friday. In it, she demanded the president-elect denounce his supporter.

As she wrote:

“Even after an election that exposed deep divisions in our country, surely we can all agree on this: The mass shooting at Sandy Hook happened. Twenty-six families, including mine, were torn apart and will never be the same. Any preposterous ideas to the contrary cannot be allowed to seep into our country’s mainstream discourse. They must be swiftly and publicly refuted.”

Of those who claim the shooting was fake, she called Jones the “most prominent popularizer” of the lie.

“A quick Google search for the phrase ‘Sandy Hook truthers’ will turn up thousands of stories about how the worst day of my life was actually an elaborate conspiracy that never happened at all,” Lafferty wrote. “It’s insanity.”

(It should be noted that while Jones has long denied the reality of what occurred at Sandy Hook, he recently released a video to clarify his position. In the video, Jones said, “I don’t know what really happened” at Sandy Hook. While Jones admitted there is proof that some people died, he claimed, “The official story of Sandy Hook has more holes in it than Swiss cheese.”)

To Lafferty, though, the issue extends beyond her personal feelings. She wrote:

“President-elect Trump will face the same kinds of tragedies President Obama has lived through. He’ll need to visit with the brokenhearted, and he’ll need to prove he’s the kind of man – and president – who can represent us all. A man who ran on a campaign to “improve our country” simply cannot embrace a man whose preposterous theories are antithetical to our shared values.”

“Conservative thinkers may interpret the Second Amendment differently than I do, but most of the conservatives I know cherish both facts and civility,” she wrote. “For example, I’ve worked closely with Sen. Patrick J. Toomey, R-Pa., and consider him to be among the kindest public servants I’ve encountered.”

Instead, it lies firmly with Trump and Jones’ relationship.

“I’ve faced the cold, hard truth of the murder of my mother, and it’s time for Trump to face one of his own. American presidents are held to higher standards than reality television stars, and our new president-elect must learn that,” wrote Lafferty, referring to Trump’s rise to televised fame as the host of NBC’s “The Apprentice.”

Given that, she placed a metaphoric call to arms to American citizens on both sides of the aisle.

“I am asking conservatives and all Americans to join me in telling President-elect Trump this: Alex Jones represents the worst of our country. It’s time to disavow the man who calls my mother’s death a hoax and not appear on his show,” she wrote.

Included in the piece was a link to a letter she has written to the president-elect. She encouraged those who agree to sign their name to it.

Trump has not responded to the letter.

On Twitter, his preferred medium for speaking to the American people, he has made no mention of Sandy Hook or Alex Jones since Lafferty’s piece was published. Instead, he’s falsely claimed that millions of people illegally voted for Hillary Clinton and that there was “serious voter fraud in Virginia, New Hampshire and California.”

Lafferty’s piece can be summed up in a single line she penned: “Mr. President-elect: You are letting me down.”