Facebook founder Mark Zuckerberg expressed regret for his failure to shut down a white miltia group that was attempting to assemble a group of armed civilians at a Jacob Blake protest in Kenosha, Wisconsin.

Prior to the demonstration, Facebook page Kenosha Guard created an event page that called for “Armed citizens to protect our lives and our property.” The page violated Facebook policies and was flagged more than 400 times, but remained on the site.

After 17-year-old Kyle Rittenhouse, an armed militia, rang fire into the crowd of protesters, severely injuring one person and killing two others, Facebook took the page down.

Zuckerberg later confessed it was a mistake, claiming there is no evidence that suggests the alleged gunman was aware of the page or the event.

“It was largely an operational mistake,” Zuckerberg said. “The contractors, the reviewers, who the initial complaints were funneled to, didn’t, basically didn’t pick this up. And on second review, doing it more sensitively, the team that’s responsible for dangerous organizations recognized that this violated the policies, and we took it down.”

He continued, “We’re going to continue to enforce our policies and continue evolving the policies to be able to identify more potential dangerous organizations and improve our execution in order to keep on getting ahead of this.”

Facebook claimed they’ve since been removing posts in support of the shooter and white militia, but according to reports from Buzzfeed, some are still existent.

Following the fatal shooting, Rittenhouse was charged and arrested with First Degree Intentional Homicide in connection with the two deaths. Prosecutors later charged him with a count for attempted intentional homicide and two counts of recklessly endangering safety. He was also charged with possession of a dangerous weapon while under the age of 18, a misdemeanor charge.

President Donald Trump has since defended Rittenhouse and is expected to meet with law enforcement in a planned visit to Kenosha.