LinkedIn co-founder Reid Hoffman apologized Wednesday for funding a group that reportedly helped to wage a disinformation campaign on social media aimed at harming Republican Roy Moore’s candidacy during Alabama’s special Senate election in 2017. Hoffman’s statement to the Washington Post marked the first time that he has acknowledged financial ties to the operation since the New York Times named him as a funder last week, though he claims that he was not aware that the group, American Engagement Technologies, was using his funds for disinformation purposes.

“I find the tactics that have been recently reported highly disturbing,” Hoffman said in the statement. “For that reason, I am embarrassed by my failure to track AET—the organization I did support—more diligently as it made its own decisions to perhaps fund projects that I would reject.” Hoffman has contributed millions of dollars to Democratic campaigns and organizations since Trump’s election.

According to the Times and the Post, a group of Democratic tech experts from various organizations, such as AET, worked together on an effort called Project Birmingham to experiment with disinformation tactics similar to those employed by Russian operatives during the 2016 presidential election. An employee from Investing in Us, a company partly funded by Hoffman, was also reportedly working on the effort. Internal documents show that those involved in the project used Facebook and Twitter to attempt to “enrage and energize Democrats” and “depress [Republican] turnout.”

Some of the methods they tested included creating false evidence that Moore was being supported by a Russian botnet and posing as Alabama conservatives with misleading Facebook pages that encouraged Republicans to vote for a write-in candidate. Hoffman describes the botnet false flag as the “most disturbing aspect” of the project.

Facebook has suspended five accounts associated with Project Birmingham, including one belonging to prominent social media researcher Jonathon Morgan, for “engaging in coordinated inauthentic behavior.” Morgan is the chief executive of the firm New Knowledge, which was a lead author of a major Senate report released last week on Russian disinformation efforts during and after the 2016 election.

“The research project was intended to help us understand how these kind of campaigns operated,” Morgan told the Times when it uncovered the existence of the project. “We thought it was useful to work in the context of a real election but design it to have almost no impact.” Project Birmingham had a $100,000 budget, presumably part of the $750,000 that Hoffman gave to AET, in a race that costed an estimated $51 million.

Alabama Sen. Doug Jones, who ultimately beat out Moore, has called for a federal probe into the project. “What is obvious now is that we have focused so much on Russia that we haven’t focused on the fact that people in this country could take the same playbook and do the same damn thing,” the senator said in a statement. “I’d like to see the Federal Election Commission and the Justice Department look at this to see if there were any laws being violated and, if there were, prosecute those responsible.”