Anti-Defamation League CEO Jonathan Greenblatt condemned Rep. Steve King (R-Iowa) for promoting white nationalist views, and he urged House Speaker Paul Ryan to take punitive action against the congressman.

In a letter sent Wednesday to Ryan, Greenblatt called on the House leader to formally censure and condemn King’s rhetoric and strip him of a House subcommittee chairmanship.

“By doing so, you will make clear that his actions were deeply offensive, wrong, and that the U.S. House of Representatives will not tolerate anti-Semitism or bigotry in any form,” he wrote.

The unusual message was delivered four days after a gunman opened fire at the Tree of Life synagogue in a predominantly Jewish neighborhood of Pittsburgh, killing 11 people and injuring six others. The ADL has logged an uptick in anti-Semitic incidents across the U.S in 2017.

Greenblatt told Ryan that he drafted the letter last week but, “after the events of this weekend, I knew that ADL could be silent no more.”

The group typically does not endorse or oppose individual political candidates, choosing to condemn King only after it became clear that the Pennsylvania attack stemmed from the same type of hateful sentiment he publicly supports. The mass shooting “reminded us that silence in the face of anti-Semitism and hate is acquiescence,” Greenblatt said.

The ADL’s letter also comes one day after Rep. Steve Stivers (R-Ohio) condemned King’s behavior in a tweet stating that “we must stand up to white supremacy and hate in all forms.” He said King’s “recent comments, actions, and retweets” were “completely inappropriate.”

Stivers, who serves as chairman of the National Republican Congressional Committee, is currently the highest-ranking member of his party to speak out against King.

King, an eight-term congressman, has in recent months used his social media platform to promote statements from white nationalists. In mid-October, he endorsed a white supremacist political candidate running for office in Canada.

In August he visited Austria, where he met with members of the far-right Freedom Party, which was founded by a former Nazi SS officer, and gave an interview to Unzensuriert, an outlet aligned with the party. King told the far-right website he believed white Europeans and Americans were being threatened by Muslim and Latino immigration and worried over declining birth rates in the West.

By doing so, Greenblatt wrote, King has given anti-Semitic organizations and individuals “the imprimatur of legitimacy that comes with meeting with a Member of Congress.”

It was “particularly outrageous,” he added, considering that the trip was funded by From the Depths, a nonprofit group dedicated to Holocaust education.

In the final days before midterm elections, the sitting congressman has lost support from corporate donors including Intel, Land O’Lakes and Purina, which all issued statements declaring King to be out of line with their values. King now faces a heated battle for re-election against Democratic challenger J.D. Scholten.