During his daily press briefing, White House Press Secretary Sean Spicer said that Adolf Hitler didn’t use chemical weapons during World War II, forgetting that Hitler did send Jews to gas chambers during the Holocaust. Later, Spicer tried to clarify his comments, saying that Hitler didn’t use gas on his own people in the “same way” that Syrian President Bashar al-Assad was doing.

“We didn’t use chemical weapons in World War II,” Spicer said. “You know, you had a… Someone as despicable as Hitler, who didn’t even sink to using chemical weapons.”

Since those comments started gaining traction on social media, a reporter asked Spicer to clarify those comments just before the end of the press conference. But the clarification only sounded worse, as Spicer referenced gas chambers and concentration camps as “Holocaust centers.”

“I think when you come to sarin gas, there was no… [Hitler] brought them into the Holocaust centers. He was not using the gas on his own people the same way that Assad is doing,” Spicer said.

Spicer later sent a statement to reporters, once again trying to clarify what he meant. “In no way was I trying to lessen the horrendous nature of the Holocaust. I was trying to draw a distinction of the tactic of using airplanes to drop chemical weapons on population centers. Any attack on innocent people is reprehensible and inexcusable,” Spicer said.

Gas chambers were used during the Holocaust. According to the U.S. Holocaust Memorial Museum, the Nazis began experimenting with the use of gas chambers in late 1939 as a way to kill multiple people at once. The Nazis established six gassing installations as part of an “Euthanasia Program” that used carbon monoxide gas. At one point, 6,000 Jews were gassed per day at Auschwitz, using Zyklon B, according to the museum.

Although Spicer said Hitler didn’t use chemical weapons on his own people like Assad, it’s estimated that 228,000 Austrian and German Jews were killed during the Holocaust.

The Holocaust Museum responded to Spicer’s gaffe with a video of what Americans found when liberating concentration camps:

The Anne Frank Center sent out the following statement:

House Minority Leader Nancy Pelosi called on President Donald Trump to fire Spicer.

The White House has had another controversy involving the Holocaust. Back on January 27 for International Holocaust Remembrance Day, the Trump Administration didn’t mention Jews in its statement. Spicer then criticized the media and critics for “nitpicking” the statement.

“The president went out of his way to recognize the Holocaust and the suffering that went through it and the people that were affected by it and the loss of life,” Spicer said in January. “And to make sure that America never forgets what so many people went through, whether they were Jews or gypsies, gays, disability.”

Spicer’s comments on Tuesday came a week after a chemical attack in Idlib Province, Syria, which the U.S. has said Assad is to blame for. According to The New York Times, the Turkish government estimates that over 100 people were killed.

The Trump Administration responded to the attack by launching 59 Tomahawk cruise missiles at the Syrian military airbase where the attack is believed to have originated from. Six Syrian soldiers were killed in the attack.

There have been international laws against the use of gas as a weapon in warfare since 1899. After gas was used during World War I, the Geneva Conventions also made it illegal to use chemical weapons, beginning in 1928.