In a hearing Tuesday, the Senate Commerce and Judiciary committees showed considerable interest in Cambridge Analytica, the firm that in 2015 lifted information from some 87 million Facebook users, without their knowledge. In his testimony, Facebook CEO Mark Zuckerberg said that was “my mistake, and I’m sorry,” but Zuckerberg also revealed data sharing of a different sort. He is collaborating with Robert Mueller’s probe, which the previous day mounted a raid on the office, home, and hotel room of President Trump’s lawyer Michael Cohen.

On Tuesday the Mueller probe first emerged in the statement of California Democrat Dianne Feinstein, who charged that “foreign actors” were using platforms such as Facebook to interfere in elections. The Russian Internet Research Agency (IRA) “ran a coordinated campaign through Facebook,” Feinstein said, with “ads and false information to harm Secretary Clinton’s campaign.” It was all a strategy for the Trump campaign, in which Russia identified which voters to target.

Zuckerberg did not address how this ad campaign might have swayed the election for Trump, but it did emerge that the Russians had purchased only $100,000 worth of ads on Facebook. Senator Tammy Baldwin said Russia had targeted her state with “divisive ads.” Zuckerberg said he would deploy new apps that would enable users to see all the ads any party had run.

Sen. Patrick Leahy, Vermont Democrat, asked Zuckerberg if special counsel Robert Mueller had subpoenaed Facebook. “Yes,” Zuckerberg said, “I am actually not aware of a subpoena. I’m aware that there may be, but we are working with them,” adding that Facebook employees had been interviewed but he had not.

The CEO whose powerful company had looked the other way at personal data lifted from 87 million users told the committees, “I want to be careful here because our work with the special counsel is confidential and I want to make sure that in an open session I’m not revealing something that is confidential.”

Sen. Cory Gardner, Colorado Republican, asked Zuckerberg if the government had ever demanded that Facebook remove a page from the site. “Yes, I believe so,” Zuckerberg said, but did not indicate the content of the page nor who, exactly, had made the demand.

Senator Ted Cruz asked Zuckerberg if Facebook is a neutral public forum. There was certain content they did not allow, hate speech, terrorist speech and so forth, the CEO said, but “our goal is not to engage in political speech.” Cruz mentioned bias and political censorship, suppression of stories on the IRS scandal, and a Trump support page that had been blocked.

Zuckerberg said Silicon Valley was “an extremely left-leaning place,” so this was a “fair concern.”

Cruz asked if Facebook had ever taken down an ad or page from Planned Parenthood, MoveOn.org, or any Democrat running for office. Zuckerberg was not aware of any such actions. Nobody was hired or fired based on politics, he said, and he was “very committed” that Facebook should be “a platform for all ideas.” Sen Thom Tillis recalled that POTUS 44 was “proud of exploiting data” in 2012, and that Facebook did nothing to stop the practice.

Senator Mazie Hirano expressed concern that ICE was using Facebook to determine whether people were criminals, terrorists, or of value to American society. The Hawaii Democrat wanted to know if Facebook plans to cooperate with ICE and the Trump administration.

“We would not proactively do that,” Zuckerberg said. Only with an imminent threat of harm, or when law enforcement presented a “valid legal request” for data would Facebook cooperate with federal immigration authorities.

Senator Cory Booker used up much of his five minutes with a sermon on America’s “dark history” of prejudice and practices such as redlining. He did not want Facebook used to surveille groups such as Black Lives Matter and Zuckerberg said he was committed to that. The CEO spoke of hiring as many as 20,000 new people and Booker asked if he would allow “civil rights organizations” to play an auditing role. “Good idea,” Zuckerberg said. “I will follow up.” The New Jersey Democrat said it was a matter of urgency because the entire tech industry “lacks diversity.”

Democrats and Republicans alike expressed concerns privacy and the way Facebook protected users’ data. Sen. Dick Durbin asked Zuckerberg if he would like the name of the hotel where he was staying to be revealed, and the CEO said he would not.

Sen Jon Tester was troubled by the Cambridge Analytica episode and asked what steps Facebook was taking so it would not happen again. Zuckerberg said he was restricting the access of app developers and investigating every app that had access to information in the past. On the other hand, Zuckerberg explained, Facebook had been hacked and “security is never a solved problem.”

Several senators said Facebook might have to be regulated and Zuckerberg said he was committed to working with Congress on “targeted regulations.”

On Wednesday the Facebook CEO testifies to the House Energy and Commerce Committee, which has already made his written testimony available.