Mark Zuckerberg

Updated at 7:35 p.m. ET

Mark Zuckerberg faced dozens of senators — and the American television audience — to take "hard questions" on how Facebook has handled user data and faced efforts to subvert democracy.

"We didn't take a broad enough view of our responsibility, and that was a big mistake. It was my mistake, and I'm sorry," the co-founder and CEO of Facebook, uncharacteristically wearing a suit, said in his opening remarks. "I started Facebook, I run it, and I'm responsible for what happens here."

mark zuckerberg capitol hill
Liam James Doyle / NPR

Facebook CEO Mark Zuckerberg is testifying on Capitol Hill to answer questions about protecting user data.

mark zuckerberg capitol hill
Liam James Doyle / NPR

Facebook CEO Mark Zuckerberg is appearing on Capitol Hill for a second day of hearings about protecting its users' data.