U.S. service members killed and wounded in Saturday’s ambush in Syria were part of the , a senior U.S. official stated.

An ISIS gunman fired an automatic weapon in the central Syrian town of Palmyra, killing two Iowa National Guard soldiers and one American civilian translator, the official noted.

Three additional U.S. soldiers were injured in the attack.

Preliminary details suggest the attacker was previously affiliated with the and had been a low-level member of the Syrian Security Forces before later joining ISIS, the official explained.

“He was not part of the official delegation being escorted by the ,” the official said. “… This would not be classified as a ‘green on blue’ incident because the Syrian gunman was not part of the U.S.-Syria partnered delegation.”

Earlier on Saturday, U.S. Central Command confirmed the deaths and injuries were a “result of an ambush by a in Syria.”

President warned that there will be “very serious retaliation” following the ambush.

“We mourn the loss of three great American patriots in Syria—two soldiers and one civilian interpreter. We also pray for the three injured soldiers, who have just been confirmed to be doing well,” Trump wrote on Truth Social.

Trump added, “This was an ISIS attack against the U.S. and Syria, in a very dangerous part of Syria that is not fully controlled by them.”

Last month, two West Virginia National Guard members were ambushed and shot near the White House in Washington, D.C., in a targeted attack that left one soldier dead.

Greg Norman contributed to this report.