(CNN/KMOV.com) -- The Department of Defense has identified three of the four Americans killed in Syria on Wednesday.
Army Chief Warrant Officer 2 Jonathan R. Farmer, 37, of Boynton Beach, Florida; Navy Chief Cryptologic Technician Shannon M. Kent, 35, of upstate New York; and DOD civilian Scott A. Wirtz of St. Louis, Missouri were killed Wednesday in the explosion in Manbij, Syria, according to the Department of Defense.
All three died "as a result of wounds sustained from a suicide improvised explosive device," according to the military.
The fourth American killed in Syria was a contractor supporting the Defense Department, according to a Pentagon spokesman. The Pentagon will not release his name since he was not military.
According to the Department of Defense, Wirtz was assigned to the Defense Intelligence Agency as an operations support specialist.
Wirtz graduated from De Smet Jesuit High School and was a decorated service member and accomplished mixed martial artist. His cousin told News 4 he always had a passion to lift other people up.
"He treated others better than he treated himself," said Wirtz's cousin Matt Shadow.
Shadow said his cousin had the heart of a teddy bear.
Wirtz' remains will arrive back in St. Louis Saturday afternoon. His wake will be held Tuesday at Ortmann-Stripanovich funeral home in Creve Coeur followed by his funeral mass at the Cathedral Basilica on Wednesday.
The bombing is still under investigation.
CNN reported Thursday that the US initial assessment is that ISIS is responsible for the bombing.
The explosion in the northern city of Manbij Wednesday killed the four Americans and at least 10 other people. Eight civilians and two fighters from the US-backed Syrian Democratic Forces were killed in the blast, a senior commander from the Manbij military council told CNN.
The US-led coalition Operation Inherent Resolve said Wednesday that the service members were "conducting a routine patrol" at the time of the explosion. Three other US service members were injured in the attack.
The attack came less than a month after President Donald Trump announced that US troops would withdraw from Syria.
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