"We didn't use chemical weapons in World War II. We had someone as despicable as Hitler who didn't even sink to using chemical weapons," Spicer said, while speaking about Syrian President Bashar Assad's chemical weapons attack last week.

He was immediately blasted for apparently forgetting about gas chambers that were used at concentration camps to kill millions of Jewish people.

"But in the way that Assad used them, where he went into towns and dropped them down to innocent into the middle of towns... I appreciate the clarification, that was not the intent," he said.

"I think when you come to sarin gas, he was not using the gas on his own people the same way that Assad is doing," Spicer said.

Then, after the briefing, he released a statement saying he was not "trying to lessen the horrendous nature of the Holocaust."

He then clarified the clarification to the clarification, saying "any attack on innocent people is reprehensible and inexcusable."

Sean Spicer just said Assad is worse than Hitler because Hitler "didn't use chemical weapons." Also, Happy Passover from the White House.

And in a well-timed tweet, the Holocaust Museum shared a video of what US armed forces saw during the liberation of a German concentration camp.

I find nothing funny about the Press Secretary bungling holocaust history. Because I'm not sure they should get the benefit of the doubt.

"I find nothing funny about the Press Secretary bungling holocaust history," Hawaii Sen. Brian Schatz tweeted. "Because I'm not sure they should get the benefit of the doubt."

"Spicer's statement is the most evil slur upon a group of people we have ever heard from a White House press secretary."

"On Passover no less, Sean Spicer has engaged in Holocaust denial, the most offensive of fake news imaginable, by denying Hitler gassed millions of Jews to death," Anne Frank Center executive director Steven Goldstein said in a statement.

Sean Spicer should be fired for saying Hitler did not use chemical weapons on "his own people.” You mean 6 million Jews don’t count?

"Sean Spicer must be fired, and the President must immediately disavow his spokesman's statements. Either he is speaking for the President, or the President should have known better than to hire him."

"While Jewish families across America celebrate Passover, the chief spokesman of this White House is downplaying the horror of the Holocaust," Pelosi said in a statement.

"Nice guy but not the right fit," he said, along with a suggestion for a replacement.

WATCH: Alex Jones re Spicer "What the hell is that from Sean Spicer? Was he being sarcastic? It shows how historica… https://t.co/KeAsUk23bt

And Alex Jones couldn't believe it when he heard what Spicer had said, even asking whether he was being sarcastic.

"Frankly, I mistakenly used an inappropriate and insensitive comment about the Holocaust and there is no comparison," Spicer said. "For that I apologize. It was a mistake to do that."

Spicer added that he wanted to apologize so his comments would not distract from President Trump's decision to take military action against the Assad regime.

"I came out to make sure we stay focused on what the president is doing and his decisive action," Spicer said. "I needed to make sure that I clarified, and not in any way shape or form or any more of an distraction from the president's decisive action in Syria and attempts he is making to destabilize the region and root out ISIS out of Syria. My goal now and then was to stay focused on Assad, and I should have, and I will continue to make sure that I stay in my lane when I talk about that."