A Citadel graduate from the class of 2007 has been killed in combat in Afghanistan, the school is reporting.

Army Sgt. Aaron X. Wittman, was killed Jan. 10 in Khogyani District, Nangarhar Province, Afghanistan.

According to the school, his unit was attacked by small arms fire while on mounted patrol.

Wittman was assigned to the 3rd Battalion, 69th Armor Regiment, 1st Brigade Combat Team, 3rd Infantry Division out of Fort Stewart, Ga.

“I’ll never forget Aaron’s humor and optimism, even in the worst of situations,” said Wesley Walker, another member of the class of ’07.

Wittman, 28, is the first U.S. casualty of 2013, and the 18th alumnus to be killed post 9/11.

Wittman was on his second combat deployment and had previously been awarded a Bronze Star and a Purple Heart.