The families of schoolchildren who were shot at Robb Elementary School in 2022 filed two lawsuits on Friday accusing Instagram, the publisher of the popular “Call of Duty” video game and a manufacturer of semiautomatic rifles of helping to train and equip the teenage gunman who committed the massacre.

The unusual lawsuits were filed on the second anniversary of the elementary school shooting, in which 19 fourth-graders and two teachers were killed in their classrooms by an 18-year-old gunman who had purchased his weapon — an AR-15-style rifle — a few days before, as soon as he was legally able.

While much of the attention in the aftermath of the shooting has been on the flawed police response, the two suits — one filed in California, the other in Texas — focus on the gunman and the companies that he regularly interacted with leading up to the shooting. Each company, the lawsuits claim, took part in “grooming” the teenager to become a mass shooter.

Together, the suits are among the most far-reaching actions to be filed in response to the escalating number of mass shootings in the United States. The California suit, which names the publisher Activision, appeared to be one of the first to go after a video game maker for helping to promote weapons used in mass shootings.

The lawsuits argue that the gun maker, Daniel Defense, would not have been able to connect with the gunman, a socially isolated teenager living in rural Texas, without the help of the technology and video game companies.

A spokeswoman for Activision said in a statement on Friday that “we express our deepest sympathies to the families” in Uvalde, but added that “millions of people around the world enjoy video games without turning to horrific acts.” The other companies did not immediately comment.

The Uvalde families are represented by Josh Koskoff, a lawyer who has previously challenged gunmakers over mass shootings. In 2022, Mr. Koskoff reached a $73 million settlement with Remington, the maker of another AR-15-style rifle that was used in the Sandy Hook elementary school shooting that left 26 people dead in Connecticut in 2012.

“Daniel Defense is a predator but can’t get to the prey without the help of these other third parties,” said Mr. Koskoff, who is also representing Uvalde families in a suit filed this week over the police response.

The families announced a $2 million settlement with the City of Uvalde earlier this week, which they reached without filing a lawsuit.

The new cases must clear significant hurdles. There is a section of federal law known as Section 230 that has largely insulated online platforms from lawsuits over content posted by others. And a 2005 federal law grants gun makers broad protection from liability for shootings.

Mr. Koskoff made use of exceptions in the 2005 law for the Sandy Hook lawsuit. That suit, like the new ones on behalf of the Uvalde families, focused on the marketing of the weapons.

Makers of violent video games have survived previous efforts to link them to real-world violence based on the graphic content of their games. The suits filed on Friday focus instead on violent first-person shooter games as a form of advertising for the weapons they depict.

Documents surfaced during the Sandy Hook case showing that there were licensing agreements between Remington and Activision, the maker behind the realistically violent “Call of Duty” franchise.

The marketing potential for real-world weapons in “Call of Duty” also figures in a suit brought in 2022 by victims of a mass shooting at a parade in Highland Park, Ill. The gunman in that case was an avid player of the game, according to that lawsuit, though Activision was not named as a defendant.

The Uvalde families are suing Activision and Instagram, as well as their parent companies Microsoft and Meta, in California because that was where the alleged conduct took place, their lawyers said.

According to the suit, the Uvalde gunman spent significant time playing “Call of Duty,” including a recent version of the game that prominently featured the rifle model sold by Daniel Defense that the gunman used.

The suit argues that the game allows players to try out realistic simulations of recognizable real-world firearms, making Activision “the most prolific and effective marketer of assault weapons in the United States.” Instagram allowed Daniel Defense to promote its products through its social media presence even though the platform formally bans firearms advertising.

“Refuse to be a victim,” one of the gun company’s Instagram posts read, with an image of a person taking an assault-style rifle out of the trunk of a car.

Meta allows firearms makers to bypass its advertising prohibitions and market directly to children, the suit argues, through “organic” content and social media influencers.

The California suit is among the first to try to link social media companies to mass shootings. In March, a similar lawsuit — accusing YouTube and Reddit of helping to equip, train and radicalize an 18-year-old white gunman who killed 10 Black people in Buffalo, N.Y. — survived an effort by the companies to have the case dismissed. (The companies are appealing.)

The intersection of social media and gun culture has become an increasing focus of gun-control advocates.

“The theory here is that they were responsible for addicting the shooter, and then, through his addiction, radicalizing him and helping to equip him to carry out this deadly attack,” said Eric Tirschwell, the top litigator for Everytown for Gun Safety, a gun-control advocacy group that is one of the firms representing the Buffalo families. The group has also been involved in litigation against Daniel Defense and police officers over the shooting in Uvalde.

Justin Wagner, a former prosecutor and the group’s senior director of investigations, said Everytown had also sought to work with social media companies to limit gun-related content. “We’ve tried to build common ground around at least protecting kids,” he said.

Mr. Koskoff, along with another lawyer, Erin Rogiers, is representing most of the families of the children who were killed or wounded in the Uvalde massacre. They filed suit in Texas against Daniel Defense, which sold the gunman his rifle online and shipped it by mail, and against the gun store in Uvalde, Oasis Outback, where the gunman picked up the rifle and bought a second gun as well.

The suit accuses Daniel Defense of violating Texas law by offering to sell the gunman a weapon before he was 18.

The filings point to an email sent to the gunman, Salvador Ramos, after he had placed the rifle he wanted, a DDM4v7, in an online “cart” on the Daniel Defense website but had yet to purchase it. He was still 17 at the time.

“Hi Salvador, are you on the fence?” the company’s email read, according to the Texas suit. “Your DDM4v7 is ready in your cart!”

Daniel Defense, a family-owned business based in Georgia, has a history of provocative advertising, and has been successful with a direct-to-consumer model for ordering military gear online with a few clicks. A small player in the booming U.S. market for AR-15-style rifles, the company promotes the quality of its weapons, which are significantly more expensive than others on the market.

According to the court filings, the company also aggressively sought to connect with new customers through social media and “Call of Duty.”

In November 2021, the gunman in Uvalde downloaded a version of the video game, titled “Call of Duty: Modern Warfare,” that featured the DDM4v7 on its opening title page, according to the California suit.

“Within a week of downloading Modern Warfare on Nov. 5, 2021, the shooter’s phone indicates a growing obsession with weapons and accessories associated with the game,” the suit says.

The lawsuit does not make clear how the plaintiffs gained access to information stored on the gunman’s phone. But the filings make use of that information, particularly for what they describe as the gunman’s search history and Instagram usage.

By December 2021, the gunman was looking into Daniel Defense guns, researching the specific model he would use in the massacre, and saving his money to purchase it, according to the suit. At the time, he was using Instagram habitually, often in the middle of the night.

According to the filings, he bought the rifle on May 16, 2022 — 23 minutes after midnight on his 18th birthday.