Lawmakers from the House Homeland Security Committee summoned the online imageboard 8chan's owner to testify before Congress and explain how insiders are working to investigate and mitigate the proliferation of violent extremist content across the site, according to a letter penned this week.

The move comes in the wake of a mass shooting that left 22 people dead and 24 more wounded at a Texas shopping center Saturday. Minutes before the attack—which is currently being investigated as an act of domestic terrorism—the alleged gunman appears to have published a manifesto filled with anti-immigrant, white supremacist sentiments to the site.

“Experts have described 8chan as a platform for amplifying extremist views, leading to the radicalization of its users,” Reps. Bennie Thompson, D-Miss., and Mike Rogers, R-Ala. wrote in the letter published Tuesday. “Americans deserve to know what, if anything, you, as the owner and operator, are doing to address the proliferation of extremist content on 8chan.”

Though it’s been mostly offline since Monday—when network infrastructure provider Cloudflare suspended its service calling 8chan a “cesspool of hate”—the site operated for years as a sort of internet forum where users could create their own message boards and post anonymously without any prior programming experience. At its peak, the platform endured content-driven controversies, even changing its URL for a period in 2015 after being reported for allegedly hosting child pornography.

But scrutiny around 8chan escalated this year as at least three gunman have reportedly used it to share their manifestos before going on violent shooting rampages.

“In April, the killer who murdered one Jewish worshiper and wounded three others at a synagogue in Poway, California, appears to have posted an anti-Semitic and racist open letter on 8chan shortly before carrying out the mass shooting,” the representatives wrote. “In March, the killer who murdered 51 Muslim worshipers and wounded 49 more at two mosques in Christchurch, New Zealand, appears to have posted on 8chan a 74-page manifesto outlining his racist, white supremacist, anti-immigrant beliefs, as well as a link to a Facebook livestream of the massacre.”

Earlier this week, the site’s original founder Fredrick Brennan also called for it to be taken down, deeming it “a complete negative to everybody except the users that are there.”

The website’s current owner who is being summoned to Congress, Jim Watkins, continued to defend the website in a YouTube video posted Tuesday. Seated in front of an image of Benjamin Franklin as “Taps” played in the background, Watkins said the site made law enforcement aware of the latest manifesto when it posted.

A U.S. Army veteran, Watkins currently lives in the Philippines and is also reportedly being investigated by their National Bureau of Investigations for 8chan’s role in disseminating violent content and supporting the spread of child pornography. Possibly due to Watkin’s unclear whereabouts, the lawmakers noted that the letter was delivered via email, mail and Twitter.

“Please provide the committee with current physical contact information for you or your authorized representative in the United States so you can retrieve communications from the Committee,” they wrote.

8chan posted Watkin’s alleged response to the letter on Twitter Tuesday night. Though he did not explicitly agree to testify, the owner said he was flying back to America to help his son prepare for the first day of school.

“Rest assured I am not an extremist,” Watkins wrote. “My telephone should work worldwide.”

A representative from the committee told Nextgov Wednesday afternoon that they cannot yet confirm whether they’ve received a legitimate response from Watkins regarding the testimony.