The U.S. Army soldier who was killed Tuesday in Afghanistan has been identified by the U.S. Department of Defense. Staff Sgt. Matthew V. Thompson died when a roadside bomb — or IED — detonated near his patrol in Helmand Province while “he was conducting dismounted operations with Afghan forces” on Tuesday, Military.com reported.

The 28-year-old was a Green Beret and assigned to Company A, Third Battalion, First Special Forces Group (Airborne), Joint Base Lewis-McChord, Washington, the Pentagon announced in a press release.

An investigation into Tuesday's attack has officially been launched.

“He was an exceptional Green Beret, a cherished teammate, and devoted husband,” Lt. Col. Kevin M. Trujillo, a commander of Special Operations Task Force-Afghanistan, said in a statement following Thompson’s death.

Thompson was on foot patrol clearing IEDs when the explosion took place, NBC News reported Tuesday.

"Our deepest sympathies go out to the families and friends of those involved," General John W. Nicholson, commander of U.S. and NATO forces in Afghanistan, said Tuesday before Thompson's identity was officially announced. "We are deeply saddened by this loss, but remain committed to helping our Afghan partners provide a brighter future for themselves and their children."

Thompson, a highly decorated soldier from Irvine, California, has been posthumously awarded the Combat Infantry Badge, a Bronze Star Medal with V device and a Purple Heart Medal. He was on his first deployment to Afghanistan when he was killed but has previously been deployed to Iraq.

Officials in Afghanistan had been increasing their calls for assistance this month over concerns that the Taliban were making significant gains in Helmand Province, Reuters reported. U.S.-led airstrikes were ramped up in late July and early this month but the American foot patrol — like Thompson's —remained on the ground.

Earlier this year the U.S. sent hundreds of troops to Helmand Province to help fortify Afghanistan military troops' efforts against the Taliban. However, U.S. troops were supposed to steer clear of any danger.

"Our mission remains the same," Colonel Michael Lawhorn, a spokesman for the U.S. command in Kabul, said, according to Reuters. "To train, advise, and assist our Afghan counterparts, and not to participate in combat operations."