Merck & Co.’s CEO resigned from President Donald Trump’s council of manufacturing executives Monday, saying “America’s leaders must honor our fundamental values” by rejecting expressions of hatred, bigotry and group supremacy. He was almost immediately attacked by Trump on Twitter.

Following a weekend of violence in Virginia involving white supremacist groups that Trump has been criticized for not taking a forceful enough stand against, Merck Chief Executive Officer Ken Frazier said “as a matter of personal conscience, I feel a responsibility to take a stand against intolerance and extremism.”

Less than an hour later, Trump tweeted in response, “Now that Ken Frazier of Merck Pharma has resigned from President’s Manufacturing Council, he will have more time to LOWER RIPOFF DRUG PRICES!”

The council has included top executives from Boeing Co., Dow Chemical Co. and Johnson & Johnson. Frazier’s resignation from the group -- the latest CEO to quit one of Trump’s high-profile executive advisory groups -- comes after a weekend of violent clashes in Charlottesville, Virginia, following demonstrations by white supremacists that resulted in one death.