Washington (CNN) -- National Public Radio's chief executive apologized to the network's employees Sunday for the way she handled the firing of news analyst Juan Williams.
"While we stand firmly behind that decision, I regret that we did not take the time to better prepare our messaging and to provide you with the tools to cope with the fallout from this episode," CEO Vivian Schiller said in a memo to NPR staff.
Williams' NPR contract was terminated Wednesday, two days after he said on Fox News' "The O'Reilly Factor" that he gets nervous when he sees people with Muslim garb on planes.
Schiller, a former CNN executive who joined NPR as president and CEO in January 2009, said Williams had made previous comments that raised questions.
"Juan's comments on Fox News last Monday were the latest in a series of deeply troubling incidents over several years," Schiller said in the memo. "In each of those instances, he was contacted and the incident was discussed with him. He was explicitly and repeatedly asked to respect NPR's standards and to avoid expressing strong personal opinions on controversial subjects in public settings, as that is inconsistent with his role as an NPR news analyst.
"After this latest incident, we felt compelled to act. I acknowledge that reasonable people can disagree about timing: whether NPR should have ended our relationship with Juan earlier, on the occasion of other incidents; or whether this final episode warranted immediate termination of his contract."
Williams criticized his former employer Sunday, saying NPR had engaged in "character assassination."
"To get fired obviously is no pleasure," Williams said Sunday on Fox News. "But then to be called a bigot and the innuendo that I'm somehow unstable was, I thought, despicable."
Schiller said after Williams' firing that "feelings that he expressed on Fox News are really between him and his psychiatrist ... but it is not compatible with the role of a news analyst on NPR's air."
Schiller later apologized for the psychiatrist reference, saying in a posting on NPR's website that the remark was "thoughtless."
Williams has signed a multi-year deal with Fox News that involves an expanded role at the network, Fox News Chairman and CEO Roger Ailes said Thursday.
"I think Americans feel there's nothing wrong in telling someone how you feel," Williams said Sunday. "To be punished for that is unfair and amounts to censorship."
The controversy started October 18, when Williams told Bill O'Reilly, "Look, Bill, I'm not a bigot. You know the kind of books I've written about the civil rights movement in this country. But when I get on a plane, I got to tell you, if I see people who are in Muslim garb and I think, you know, they are identifying themselves first and foremost as Muslims, I get worried. I get nervous."
He continued, "Now, I remember also that, when the Times Square bomber was at court, I think this was just last week, he said the war with Muslims -- America's war -- is just beginning. The first drop of blood. I don't think there's any way to get away from these facts.
"But I think there are people who want to somehow remind us all -- as President Bush did after 9/11 -- it's not a war against Islam."
Williams told O'Reilly, "You've got to be careful" to point out that there are good Muslims. He noted that Americans don't blame Christians for the actions of Timothy McVeigh in the Oklahoma City bombing.
Nihad Awad, executive director of the Council on American-Islamic Relations, called Williams' remarks "irresponsible and inflammatory ... and they should not pass without action by NPR." But he told ABC News that he did not believe Williams should have been fired.
Schiller said Sunday she "deeply" regretted how she handled and explained the firing.
"In any event, the process that followed the decision was unfortunate -- including not meeting with Juan in person -- and I take full responsibility for that," she said in the memo. "We have already begun a thorough review of all aspects of our performance in this instance, a process that will continue in the coming days and weeks."