Top Silicon Valley officials are set to appear before Congress tomorrow to discuss the spread of violent content online after a video stream documenting a white nationalist’s massacre of 50 Muslim worshippers in New Zealand proliferated on their platforms.

On March 19, House Homeland Security Committee Chairman Bennie Thompson (D-MS) sent a letter to executives at YouTube, Twitter, Facebook, and Microsoft, asking them to brief his committee about their response to the video’s dissemination and what their plans are to ensure that it will not happen again.

A spokesperson for the committee told The Daily Beast that representatives from those four tech giants have agreed to come to Congress on Wednesday for a closed-door briefing on the topic.

If Thompson’s initial letter was any indication, lawmakers aren’t pleased with how tech companies handled the New Zealand shooter’s video. While the shooter live streamed his attack on Facebook, copies of the video were subsequently posted to YouTube, Twitter, and elsewhere. From there, the video was spread further across the internet.

Facebook said publicly that it removed 1.5 million copies of the video on its platform, while YouTube said it removed an “unprecedented amount.”

But it took the companies a long time to take down those videos—too long, in the eyes of New Zealand authorities and, clearly, some members of Congress. According to an ABC News report, copies of the violent stream were available on YouTube up to at least to eight hours after the attack.

Thompson, in his letter, noted that tech companies have formed a joint task force to address the spread of content from Islamist terror groups like ISIS but have not done the same for other kinds of violent extremists. “It is clear from the recent pattern of horrific mass violence and thwarted attempts at mass violence — here and abroad — that this is not merely an American issue but a global one,” he wrote.

“You must do better.”