The National Security Council said in a statement that it was looking into how a journalist’s number was added to the chain in the Signal group chat. In addition to Defense Secretary Pete Hegseth, it included Vice President JD Vance, Secretary of State Marco Rubio and Tulsi Gabbard, Trump’s director of national intelligence.

Goldberg said he received the Signal invitation from Mike Waltz, Trump’s national security adviser, who was also in the group chat.

Hegseth in his first comments on the matter attacked Goldberg as “deceitful” and a “discredited so-called journalist” while alluding to previous critical reporting of Trump from the publication. He did not shed light on why Signal was being used to discuss the sensitive operation or how Goldberg ended up on the message chain.

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The administration’s handling of the highly sensitive information was swiftly condemned by Democratic lawmakers. Senate Democratic leader Chuck Schumer called for a full investigation.

“This is one of the most stunning breaches of military intelligence I have read about in a very, very long time,” Schumer, a New York Democrat, said in a floor speech Monday afternoon.

The handling of national defense information is strictly governed by law under the century-old Espionage Act, including provisions that make it a crime to remove such information from its “proper place of custody” even through an act of gross negligence.