Mr. Trump’s administration studied the issue previously and came to no significant conclusion about connections between mass shootings and violent video games.

After last year’s shooting at Marjory Stoneman Douglas High School, the Trump administration convened a federal commission on school safety. The commission’s final report downplayed the role of guns in school shootings. Instead, it called for improving mental health services, training school employees in firearm use and rolling back rules developed during the Obama administration that were aimed at ensuring minority children weren’t unfairly disciplined by schools.

The commission’s 180-page report devotes a chapter to what it calls “violent entertainment,” including video games. After hearing from a variety of researchers and other experts, the commission officially recommended that state and local educational agencies have internet safety measures in place, and the enforcers of voluntary ratings systems — such as the Motion Picture Association of America’s practice of assigning ratings like “PG-13” and “R” to movies — should review and improve their policies.

It made no specific recommendation in regards to video games.

In some cases, the perpetrators of mass shootings are quite clear about their motivations. On Saturday, a 2,300-word manifesto appeared online minutes before the shooting in El Paso, Tex., in which 21 people were killed. The second line of the hate-filled, anti-immigrant manifesto says the attack “is a response to the Hispanic invasion of Texas.”

Law enforcement officials were investigating whether it was written by the shooter. They were interviewing the suspect, Patrick Crusius, a 21-year-old white man who lived about a 10-hour drive from the Walmart where the shooting took place.

Video games are, however, mentioned in the manifesto. “Don’t attack heavily guarded areas to fulfill your super soldier COD fantasy,” it advised, referring to the popular Call of Duty franchise of games in which players usually embody the roles of soldiers.

People who commit mass shootings sometimes identify as video gamers, but James Ivory, who studies media and video games at Virginia Tech, cautioned to be aware of the base rate effect. Of course some mass shooters will have played violent video games, he said — video games are ubiquitous in society, especially among men, who are much more likely to commit mass shootings.