Here's a look at previous deaths among U.S. service members in Syria:
Nov. 24, 2016: Navy Senior Chief Petty Officer Scott Cooper Dayton, 42, of Woodbridge, Virginia, was killed in an improvised explosive device blast near the northern Syrian town of Ayn Issa, becoming the first American casualty in combat in the fight against IS in Syria.
March 28, 2017: Air Force Staff Sgt. Austin Bieren, 25, of Umatilla, Oregon, died in northern Syria in a non-combat-related incident while deployed in support of combat operations.
May 26, 2017: Army Spc. Etienne J. Murphy, 22, of Loganville, Georgia, died in Al-Hasakah, Syria, of injuries sustained during an incident related to a vehicle rollover, according to a statement from the Department of Defense.
March 30, 2018: U.S. Army Master Sgt. Jonathan J. Dunbar was killed by a roadside bomb attack in Syria along with a British service member.