Washington — White House national security adviser Jake Sullivan on Sunday condemned Russia for what he called the “shocking and horrifying” killing of an American journalist in Ukraine by Russian forces and vowed the U.S. would respond with “appropriate consequences” once the Biden administration obtains more information about the death.

“This is obviously shocking and horrifying, and I’ve just learned about it as I came onto air here, so I will be consulting with my colleagues, we’ll be consulting with the Ukrainians to determine how this happened and then to measure and execute appropriate consequences as a result of it,” Sullivan told “Face the Nation” when asked about the consequences would be for the Russians killing an American.

“This is part and parcel of what has been the brazen aggression on the part of the Russians where they have targeted civilians, they have targeted hospitals, they have targeted places of worship and they have targeted journalists,” he continued.

The head of Kyiv’s regional police force, Andriy Nebytov, said Sunday that a 51-year-old American journalist, believed to be Brent Renaud, was killed and a colleague was injured by Russian forces in Irpin, Ukraine. Nebytov posted photos on Facebook purportedly of Renaud’s body, his U.S. passport and credentials from the New York Times.

The Times said in a statement it is “deeply saddened” to hear of Renaud’s death and said he was a “talented filmmaker” who contributed to the Times over the years. Renaud was not, however, on assignment for the Times in Ukraine.

“Early reports that he worked for Times circulated because he was wearing a Times press badge that had been issued for an assignment many years ago,” a spokesperson for the paper said.

Sullivan said the Biden administration will be tracking developments regarding the attack on the journalists “very closely and responding accordingly.”

The attack on foreign journalists documenting the war in Ukraine comes after Russia fired more than 30 cruise missiles at a military training base located less than 15 miles from Ukraine’s border with Poland, a member of NATO. The strike left 35 people dead, and the training facility is the most westward target hit by Russian forces so far in the 18 days since they invaded Ukraine.

Sullivan warned Sunday that if there is a military attack on NATO territory, it would lead to the invocation of Article 5, which provides that if a NATO ally is the victim of an armed attack, each country in the 30-member alliance will consider it an armed attack against them all and take action.

“If Russia attacks, fires upon, takes a shot at NATO territory, the NATO alliance would respond to that,” he said.

Sullivan noted that President Biden has been clear that the U.S. would work with allies “to defend every inch of NATO territory, and that means every inch.”

Russia’s continued action in Ukraine and rhetoric accusing the U.S. and Ukraine of using chemical or biological weapons has heightened concerns that Russian forces could use chemical weapons.

Sullivan said the U.S. can’t “predict a time or place” of a chemical weapons attack, but warned Russia is preparing for such a move and will try to “pin the blame elsewhere.”

“Nobody should fall for that,” he said. “That is why we’ve gone out so decisively at the United Nations Security Council and elsewhere to rob the Russians of the capacity to pin this on anyone other than themselves. And as the president said on Friday, if in fact the Russians do use chemical weapons in Ukraine, they will pay a severe price.”

Sullivan said the use of weapons of mass destruction by Russia would be a “shocking additional line that [Vladimir] Putin is crossing in terms of his assault on international law and international norms, his assault on the human rights and human dignity of the people of Ukraine.”