It was just weeks after 26 people were gunned down at Sandy Hook Elementary School when Lenny Pozner first saw people speculating online that the rampage had been staged, with crisis actors responding to a fake attack.

His 6-year-old son, Noah Pozner, who had gone to school that morning in a Batman sweatshirt, was one of the 20 children killed in Newtown, Conn., in December 2012.

Before the funerals had even concluded, an online conspiracy theory made targets of grieving family members. Strangers hurled insults at Pozner, asking how much he got paid to play his part in the government-sponsored hoax. They used photos of his son, with his tousled brown hair and round cheeks, on websites claiming the shooting was faked to generate urgency for gun-control laws. Then came the death threats.

It was the stuff of madness. But in a time of madness — in a world in which science can be dismissed as political ploy and videos might reflect truth or fabrication — Pozner found himself having to fight to prove, over and over, that his son had lived, and his son had died.

June marked a turning point: He won a lawsuit against the editors of a book that claimed no one was killed in the attack. A Wisconsin judge issued a summary judgment against James H. Fetzer and Mike Palecek, finding they defamed Pozner with statements that his son’s death certificate was a ruse.

In a separate settlement, the book’s publisher agreed to stop selling it.

Pozner has been trying to reclaim his son’s history for years.

To combat the hoaxers, he has used earnest pleas, official complaints, rhetoric, lawsuits. He and volunteers from the HONR Network, a nonprofit organization he founded to combat the harassment, have challenged targets obscure and gargantuan, from lone conspiracy theorists to companies as powerful as Google.

Increasingly, families of others killed at Sandy Hook have started fighting back publicly. Relatives and prosecutors have brought at least nine cases against hoaxers, according to an attorney for a group of plaintiffs, including three in Connecticut consolidated by the court. In recent months, family members have started seeing real gains in a fight most were reluctant to wage.

In Connecticut, there was a turning point, too, with a judge imposing sanctions on Alex Jones, who runs the conspiracy-driven Infowars website, and agreeing to a trial in a defamation case.

Litigation is incredibly invasive and inconvenient and expensive, said Jake Zimmerman, an attorney for Pozner. It can also be a powerful weapon against rumor and innuendo, with rules of evidence and civil procedure built over hundreds of years.

“You have to rely on documents instead of things like hearsay,” he said.

They handed the judge in the Wisconsin case Noah Pozner’s death certificate, with its raised seal, to disprove the allegation in the book that images of the certificate had been altered or faked.

They turned over 70 pages of pediatric medical records.

They asked the court to appoint an independent expert to compare a sample of Lenny Pozner’s DNA with a sample, obtained from the medical examiner, of Noah Pozner’s DNA.

“Unimpeded conspiracy theories distort truth and erase history,” Pozner said afterward. “They dehumanize victims. People like Fetzer who hide behind their computer screen and terrorize people grappling with the most unimagined grief, were put on notice,” he said, as were social media companies that allow their platforms to be weaponized.

Fetzer told The Washington Post in an email that he was dumbfounded by the ruling in Wisconsin. “The decision by the Court was improper on multiple grounds and I am going to do whatever I can to correct the record. The American public has been played by one fake event after another and deserves to know the truth,” Fetzer wrote.

The lawsuit against him was never about defamation, Fetzer wrote online, “but about suppressing freedom of speech and freedom of the press. The Deep State does not want the American people to grasp the extent to which they have been bamboozled by their own government.”

In three cases against Jones in Texas — including one brought by Pozner and Noah’s mother, Veronique De La Rosa — Mark Bankston, an attorney for the parents, said Jones’s obsession with Sandy Hook had created “a seven-year open wound” for the families.

In one case, Neil Heslin sued Jones and other defendants for defamation in 2017 for statements made on Jones’s Infowars website that Heslin was lying when he recalled holding his son’s body after the shooting.

In another, Scarlett Lewis seeks damages because of the false narrative promoted on Infowars, with stories mocking her and other parents of victims as liars.

De La Rosa and Pozner’s case accuses Jones of defamation and intentional infliction of emotional distress for harassing families for years and for claiming De La Rosa was an actor in a faked interview on CNN about the shooting.

A judge has denied motions to dismiss the cases brought by Heslin, De La Rosa and Pozner, and Lewis, and the defendants have appealed those decisions.

Robert Barnes, an attorney for Jones in the Texas cases, said they could prove precedent-setting, raising important First Amendment issues.

“Is emotional harm more important to protect than free speech?” Barnes said. “We believe protecting speech matters more than emotional safety.”

The shooting happened on a Friday. By Sunday, Robbie Parker, whose 6-year-old daughter, Emilie, was killed in the attack, knew there were videos accusing him of being a crisis actor, because people were posting them on a social media page that friends created as a memorial to Emilie.

The page was quickly inundated. Parker was getting emails to his personal and work addresses. By the time of Emilie’s funeral, he had already been threatened.

The conspiracy theories affected much of Newtown. The school board and other agencies received relentless demands for public records. FBI agents, emergency workers and others were accused of participating in the hoax. Strangers were showing up in town and videotaping children.

At first, Parker was confused, assuming the wild theories would quickly subside. He didn’t realize how social media would fuel those ideas and sustain them, providing a shroud of anonymity and making it easy for ideas to go viral. “They were able to do a lot of really harmful things with no understanding of the consequences of it and without any threat of being held responsible,” he said.

Years later and thousands of miles from Newtown, he was walking toward a hotel in Seattle when a stranger stopped him and began yelling and cursing about a hoax.

Parker thought he had composed himself — and made sure the man was no longer following him — before he went to the hotel room where he, his wife and young daughters were staying. But as soon as his wife saw his face, he broke down, hyperventilating and crying, he said. They closed themselves in the bathroom to talk about what had happened and how to explain it to their daughters.

It wasn’t until the 2018 shooting at Marjory Stoneman Douglas High School in Parkland, Fla., that the path forward became clear.

A friend asked Parker to talk to parents whose daughter had died in the Florida shooting. The mother, in shock, told him people were harassing the victims’ families in Parkland and claiming no one had died.

That’s when he realized, he said, that a lawsuit might not only help protect the memory of his daughter and keep his family safe, but also prevent other families from being victimized anew.

The Newtown families were bewildered at first, said Chris Mattei, an attorney for those families. Then many hoped it would fade away. Instead, it intensified, he said, inflamed by Jones’s enormous public platform on Infowars. The families’ lawsuit filed in Connecticut argues that the stories Jones promotes are designed to create an audience and a market for his retail store that sells nutritional supplements and other items.

The case was brought by eight families of people killed at Sandy Hook and an FBI agent who responded to the scene. It was filed against Jones, several corporate entities, a conspiracy theorist who has been a guest on Infowars and his associate.

In June, Superior Court Judge Barbara Bellis in Connecticut imposed sanctions on Jones, citing two reasons. First, she said his legal team failed to produce several documents, despite repeated orders that they be provided. Second, the judge referenced what she described as a 20-minute “deliberate tirade and harassment and intimidation” on Jones’s broadcast about the lawsuit, Mattei and the discovery of child pornography that had been included in electronic documents Jones’s attorneys submitted.

Bellis criticized the defendants’ delays in producing documents and noted that electronic records, when provided to the court, included images of child pornography.

She took sharp exception to Jones’s response to that on Infowars.

If Jones believed those images were planted in an attempt to frame him, she wrote, he should have alerted authorities and filed a motion alerting the court; his lawyers could have asked the lawsuit to be dismissed for that reason.

“What is not appropriate,” Bellis wrote, “what is indefensible, unconscionable, despicable, and possibly criminal behavior is to accuse opposing counsel, through a broadcast, no less, of planting child pornography, which is a serious felony.”

Bellis ordered Jones to pay some of the plaintiffs’ legal fees as part of the sanction and told the defendants they could not pursue a motion to dismiss. She set a trial date for November 2020.

Jones’s attorneys have asked the Connecticut Supreme Court to review Bellis’s decision.

Norm Pattis, an attorney for Jones, said an important principle is at stake in the case.

“Our contention is he violated no law in offering the opinions he did. To silence him because his views were unpopular might be easy in this case, given the public sympathy for Sandy Hook families,” Pattis said, but that could erode First Amendment protections. “Defending Mr. Jones’s right to speak involves defending all of our right to speak.”

Jones no longer doubts the shootings took place but had the right to ask questions about what happened, Pattis said.

People turn to Jones because a crisis of legitimacy afflicts the country, Pattis said, with suspicions about information from the government and the media.

“People don’t know who to believe,” Pattis said.

The rumors continue to spread. In late June, Parker’s sister called in tears because someone was sending her social media messages with links to videos, demanding to know why her brother had participated in a hoax.

When he recalls Emilie and the other victims, Parker thinks of “just how innocent and beautiful and loving they were. For their memories and their lives to be tarnished and to be used in this way is one of the most . . .” he said, trailing off.

The tragedy isn’t just that their lives were cut short, he said. Their lives also have been redefined by strangers.

Even in those first weeks and months after the shooting, in a haze of grief and shock, Pozner knew what was happening online. He had seen conspiracy theories grow and spiral online, drawing in the curious and the skeptical. He didn’t know yet what it was to be trapped in one.

He sent an email to Jones: “Haven’t we had our share of pain and suffering?”

In the wrenching, chaotic year that followed, he knew the lies continued, but he had no emotional bandwidth to respond. Bit by bit, he started to try to reclaim the truth. He posted photos of Noah, his mother and sisters. There he is, a chubby-cheeked little boy, splashing in a pool with floaties; curled up with his sisters listening to Pozner read; playing in the snow; eating a toffee apple; holding a bouquet of dandelions, beaming.

When people used the photos of Noah in blog posts claiming a hoax, Pozner and volunteers from the HONR Network asked that the pictures be removed, relying on copyright law when needed.

In December 2015, when President Trump was campaigning for office, he praised Jones’s “amazing” reputation while appearing on his show.

That same month, De La Rosa and Pozner wrote an opinion piece in the South Florida Sun-Sentinel: It had been three years since their son died, they wrote, and people continued to badger them for proof of Noah’s existence.

They asked Florida Atlantic University officials to fire James Tracy, a professor who kept a blog with claims that the Newtown shooting had been staged.

They had filed a police report claiming harassment, they wrote, after Tracy sent a certified letter demanding proof they were Noah’s parents.

The university started termination proceedings against Tracy in January 2016.

That month, Pozner received threatening messages warning him death was imminent. “I was stunned,” he said. “I could hear her voice and the vitriol and hate in her words.”

In 2017, a Florida woman, Lucy Richards, was sentenced to five months in prison for making death threats against Pozner.

Pozner moves often and tries to keep his address secret.

Pozner and the HONR Network have been pushing companies to be more responsive to complaints about conspiracy theories, with change coming from major platforms such as WordPress, Facebook and Google. In June, YouTube announced that it would remove content denying the occurrence of well-documented violent events such as Sandy Hook.

Story by story, site by site, year after year, Pozner has been working to restore the truth about his son. If the hoax idea is a brush fire, he wants to control the burn — not extinguish it so no one can hear the idea, but limit its spread and destructiveness.

Book publisher David R. Gahary thought he knew all about Lenny Pozner, because of what he had read online.

He said his company, Wrongs Without Wremedies, was willing to publish the book “Nobody Died at Sandy Hook” because he doesn’t think anyone should have the right to tell people what they should read. There were anomalies in the scenes from the aftermath of Sandy Hook, he said, and it was an important event because of people’s distrust of the government.

On May 28 at a law firm in Madison, Wis., Gahary sat at a table across from Pozner from 9 a.m. until after 6 p.m., as Pozner answered questions in a deposition.

The more he listened, he said, the more he thought Pozner was a normal person. Not a smooth talker. “Just a regular guy,” he said, “who’s telling the truth.”

At the end of the day, Gahary shook Pozner’s hand and apologized. He offered condolences for Noah’s death.

“Lenny Pozner was right,” Gahary said. “Real people are getting hurt.”

Jennifer Jenkins contributed to this report.