Two U.S. service members and one U.S. civilian were killed Saturday when an ISIS gunman ambushed them in central Syria, according to U.S. Central Command. Three additional service members were wounded in the attack.

The shooting occurred in the city of Palmyra, roughly a year after the fall of former Syrian President Bashar al-Assad and the lifting of U.S. sanctions on the country.

President Trump said on Truth Social that Syrian President Ahmed al-Sharaa was “extremely angry and disturbed” by the attack and warned that there would be “very serious retaliation.”

Defense Secretary Pete Hegseth said the gunman was killed by partner forces following the ambush.

“If you target Americans — anywhere in the world — you will spend the rest of your brief, anxious life knowing the United States will hunt you, find you, and ruthlessly kill you,” Hegseth wrote on social media.

Pentagon spokesman Sean Parnell said the attack took place as the troops were concluding a meeting with local leaders as part of a mission supporting counterterrorism operations in the region.

Since October, CENTCOM has said U.S. forces have “advised, assisted, and enabled” more than 22 counter-ISIS operations alongside partners in Syria, resulting in five ISIS fighters killed and 19 captured.

Parnell said the ambush remains under investigation.