Senate Armed Services Committee ranking member Jack Reed (D-RI) encouraged a “very aggressive” response to the ISIS attack that killed three Americans, including two U.S. Army soldiers, in Syria on Saturday.

An ISIS gunman on Saturday opened fire on American and Syrian troops in Palmyra, Syria, who were conducting a leader engagement as part of an counter-ISIS and counterterrorism operation in the region, according to chief pentagon spokesman Sean Parnell. President Donald Trump promised “very serious retaliation” following the attack.