The founder of the Free Gaza Movement, which has dispatched flotillas of ships attempting to break Israel’s naval blockade of the Gaza Strip, tweeted that Zionists were responsible for the Holocaust, then apologized.

Greta Berlin then tweeted that she meant to post the tweet to her private Facebook account rather than the organization’s Twitter account.

The original tweet, posted September 30 from @freegazaorg, read that “Zionists operated the concentration camps and helped murder millions of innocent Jews.” It linked to a video of Eustace Mullins, a conspiracy theorist, claiming that the word “Nazi” combines the words “National Socialist” and “Zionist.” Mullins died in 2010.

“I posted it from Facebook, not realizing that my private account was connected to the FG account. I apologise,” Berlin tweeted.

Although the Free Gaza Movement deleted the tweet, Avi Mayer of the Jewish Agency for Israel posted a screenshot of it on Monday, according to the National Post.