According to a senior U.S. official speaking to Fox News, the U.S. service members involved in the deadly ambush in Syria on Saturday belonged to the Iowa National Guard.

The attack, which occurred in the central Syrian town of Palmyra, was carried out by an ISIS-affiliated gunman wielding an automatic weapon. The assault resulted in the deaths of two Iowa National Guard soldiers and an American civilian translator.

In addition to the fatalities, the attack left three other U.S. soldiers injured.

U.S. forces are known to conduct patrols in northeastern Syria, particularly in the city of Qamishli located in the Hasakeh province. This activity was documented as recently as January 9. (Photo credit: Delil Souleiman/AFP via Getty Images)

Initial findings indicate that the assailant had previous ties to the Syrian government forces, having served as a minor member of the Syrian Security Forces before aligning with ISIS, the official reported.

The official clarified, “The attacker wasn’t part of the official delegation under U.S. and Syrian troop escort, thus this incident doesn’t classify as a ‘green on blue’ attack since the Syrian gunman wasn’t within the US/Syrian partnered group.”

President Donald Trump attends the 126th Army-Navy Game between the Army Black Knights and the Navy Midshipmen, Saturday, in Baltimore, Md.  (Tasos Katopodis/Getty Images)

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

President Donald Trump 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. Likewise, we pray for the three injured soldiers who, it has just been confirmed, are doing well,” Trump wrote on Truth Social. 

U.S. Army soldiers in northeastern Syria.  (John Moore/Getty Images)

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.