President Donald Trump ordered military strikes on Syria in response to a deadly chemical weapons attack on the rebel-held town of Douma.

Trump announced in a Friday night press conference that a combined operation in collaboration with France and the United Kingdom was underway.

Trump had spoken to both French President Emmanuel Macron and British Prime Minister Theresa May this week about a coordinated response, according to the White House.

Trump had called the weekend attack, which killed at least 70 people, “sick” and “atrocious,” and said Syria and its allies Russia and Iran would “pay a price.”

“If it’s the Russians, if it’s Syria, if it’s Iran, if it’s all of them together, we’ll figure it out,” Trump said on Monday. “We cannot allow atrocities like that. … Everybody’s going to pay a price.”