The Army on Monday identified the two American soldiers who were killed in Palmyra, Syria, over the weekend as Sgt. Edgar Brian Torres-Tovar, 25, of Des Moines, Iowa and Sgt. William Nathaniel Howard, 29, of Marshalltown, Iowa. Both were members of the Iowa National Guard. 

A civilian interpreter was also killed in the attack. The Pentagon said an ISIS gunman ambushed the two guardsmen and the interpreter in Saturday's attack.

In a statement, Iowa's Gov. Kim Reynolds wrote, "Sgt. Howard and Sgt. Torres-Tovar served our state and nation with honor, and in doing so, gave the ultimate sacrifice. We are grateful for their service and deeply mourn their loss." 

Reynolds ordered flags across Iowa to immediately be flown at half-staff until sunset on the day of their funerals. 

Torres-Tovar, Howard and the interpreter were killed while they were supporting a "key leader engagement" as part of the counter-ISIS mission, according to Pentagon spokesperson Sean Parnell. Three U.S. service members were injured in the attack, and the gunman was killed. 

A Pentagon official says the U.S. currently has about 1,000 U.S. forces in Syria to counter ISIS. 

In a social media post after the attack, President Trump vowed "very serious retaliation." 

In remarks to reporters before leaving the White House for the Army-Navy football game Saturday, Mr. Trump said, "We mourn the loss of three great patriots in Syria. You know how it happened — it was an ambush, terrible. We also have three wounded. They seem to be doing pretty well, but we mourn the loss." 

These are the first U.S. troop deaths in Syria since the fall of President Bashar Al Assad last year. President Trump said Syria's new president, Ahmed al-Sharaa, is "devastated by what happened — this was an ISIS attack on us and Syria."