to testify november 18th and it started. they built a mock hearing room. he worked hard to prepare and was ready. that was as high stage as it gets. facebook s ceo, mark zuckerberg, just hours away from testifying. it s all historic, the way it was for the tobacco execs in 1994. they had to bring in extra row of chairs for the senators because there was so much interest. we re listening. america is listening, and quite possibly, the world is listening, too. reporter: and wondering could zuckerberg, who historically had a hard time with high pressure public moments deliver. we didn t take a broad enough view of our responsibility. that was a big mistake. it was my mistake, and i m sorry. i started facebook. i run it, and i m responsible for what happens here.