Merck CEO Kenneth Frazier resigned Monday from the president's American Manufacturing Council in protest of President Donald Trump's response to white supremacist violence in Charlottesville, Virginia, and Trump immediately blasted the drug executive on Twitter.

"As CEO of Merck and as a matter of personal conscience, I feel a responsibility to take a stand against intolerance and extremism," Frazier, the only African American CEO of a major pharmaceutical company, wrote in a tweet.

Merck CEO Tweet

Merck declined to comment further.

Shortly afterward, Trump responded by saying that in light of the resignation, Frazier will have more time to "LOWER RIPOFF DRUG PRICES!"

Trump Tweet

Later Monday, the president doubled down on his criticism of Merck. He called the pharmaceutical company " a leader in higher & higher drug prices while at the same time taking jobs out of the U.S."

@realDonaldTrump: .@Merck Pharma is a leader in higher & higher drug prices while at the same time taking jobs out of the U.S. Bring jobs back & LOWER PRICES!

Merck was one of the companies that partnered with the White House in its initiative to manufacture pharmaceutical glass packaging in the United States. When it was announced last month, Trump said the partnership between Merck, Pfizer and Corning would "create thousands of American manufacturing jobs."

A rally by hundreds of white nationalists in Virginia took a deadly turn on Saturday when a car plowed into a group of counter-protesters and killed at least one person. A white supremacist has been charged.

At a news conference on Sunday, Trump denounced what he called an "egregious display of hatred and bigotry" displayed by antagonists "on many sides." That drew an immediate backlash from people who felt Trump had not taken a strong enough stance against bigotry and extremism, lumping the counter-protesters in with the white supremacist groups.

On Monday, as the pressure against him escalated, Trump held a press conference where he strengthened his comments regarding the incident.

"Racism is evil," Trump said. "And those who cause violence in its name are criminals and thugs, including the KKK, neo-Nazis, white supremacists and other hate groups that are repugnant to everything we hold dear as Americans."