Story highlights Hillary Clinton told ABC News Tuesday she is "sorry" for using a private email server

Clinton also got emotional when discussing the campaign and her late mother

New York (CNN) Democratic presidential front-runner Hillary Clinton said Tuesday she is "sorry" for using a private email server, going further than ever before to express remorse for the controversy that has rocked her campaign.

"I'm sorry about that," Clinton said in an at-times emotional interview on ABC News' "World News Tonight with David Muir," acknowledging that she should have used separate accounts for work and personal business. "I take responsibility and I am trying to be as transparent as I possibly can."

Clinton later issued a slightly different apology in the interview, saying she was "sorry that it has raised all these questions."

The former first lady also posted a personal apology on Facebook Tuesday night, saying, "I wanted you to hear this directly from me: Yes, I should have used two email addresses, one for personal matters and one for my work at the State Department. Not doing so was a mistake. I'm sorry about it, and I take full responsibility."

She also added, "I know this is a complex story. I could have -- and should have -- done a better job answering questions earlier. I'm grateful for your support, and I'm not taking anything for granted."

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