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Three of the four Americans killed by an explosion in Syria on Wednesday were a soldier, a sailor and a civilian working for the Defense Department.

Army Chief Warrant Officer Jonathan R. Farmer, 37, Navy Chief Cryptologic Technician Shannon M. Kent, 35 and Scott A. Wirtz were identified by the Department of Defense as three of the Americans killed while "conducting a routine patrol" in the Syrian city of Manbij, near the Turkish border.

The fourth American killed in the blast has not been identified. The Department of Defense said Wednesday that the person was a contractor supporting the department.

Jonathan R. Farmer

Farmer joined the Army in 2005 and had served on six overseas combat tours. He was 5th Group Special Forces, and heavily decorated. Among his numerous awards was a Purple Heart.

Farmer, from Boynton Beach, Florida, is survived by his parents, his wife and four kids.

Shannon M. Kent

Kent enlisted in the Navy in 2003.

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"She was a rockstar, an outstanding Chief Petty Officer, and leader to many in the Navy Information Warfare Community,” said Cmdr. Joseph Harrison, the commanding officer of Kent's base.

Kent was from upstate New York.

Scott A. Wirtz

Wirtz was an operations support specialist for the Defense Intelligence Agency.

He had served in the Navy from 1997 to 2005, spending a majority of that time in the SEAL unit. He had been deployed to the Middle East with the DIA at least three times since he started working for the department in 2017.

Wirtz was from was from St. Louis, Missouri.

Three other U.S. service members were also injured in the explosion, according to a statement from Central Command.

ISIS claimed responsibility for the attack through recognized social media accounts, claiming a suicide bomber wearing an explosive vest attacked coalition forces. ISIS did not immediately produce evidence to support the claim.

American defense officials said that despite the claim of responsibility by the Islamic State, which is also known as ISIS, there has been little to no ISIS presence in Manbij in months, and the terror group sometimes falsely claims responsibility for attacks.

Wednesday’s killing of two U.S. service members was the single deadliest day for American forces in Syria.

The attack came weeks after President Donald Trump announced in a tweet on Dec. 19, that U.S. troops would withdraw from Syria immediately.

Trump said the U.S. had “defeated ISIS in Syria,” adding that was the “only reason” to have troops on the ground there. There are 2,000 American troops in Syria.

The announcement sent shockwaves through the region and led to the resignation of Defense Secretary James Mattis and the top U.S. envoy to the anti-ISIS coalition. It also led to major criticism that the U.S. was abandoning its local Kurdish allies amid Turkish threats of an imminent attack.

Administration officials later said troop removal will happen more slowly.