Citadel graduate Aaron X. Wittman became the 18th alumni lost in the post-9/11 war on terror, killed during a fight with enemy forces last week in Afghanistan.

The loss was an extra-heavy blow to the tight-knit Citadel family as Wittman’s father, brother and sister-in-law all had been members of the school’s Corps of Cadets before him.

Wittman, an Army sergeant from Chester, Va., south of Richmond, also was the first U.S. fatality of 2013 in the Afghan war zone.

Friends remembered the 28-year-old as someone who favored the odd prank, was happiest pumping iron in the gym, and remained committed to the school’s principles of discipline, service and sacrifice.

“He wanted to serve his country and be where the action is,” Maj. Ken Boes, one of Wittman’s school advisers from his time in the corps, said Monday.

“He wanted to do the right thing,” Boes added. “That was Aaron.”

Wittman, Class of 2007, was killed Thursday in Khogyani District, Nangarhar Province, Afghanistan. According to reports, his unit was attacked by small-arms fire while on a mounted patrol.

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

Wittman was on his second combat deployment and had previously been awarded a Bronze Star and a Purple Heart. He is the school’s first alumni loss tied to military action since June.

The family’s lineage at the school ran deep. His father, retired Army Maj. Duane L. Wittman was a 1975 graduate. His brother, Marine Corps 1st Lt. Nicholas R. Wittman, graduated in 2003. His sister-in-law, Marine Corps 1st Lt. Rikki Felts Wittman, graduated in ’04, the school said.

Citadel alumni serving in Afghanistan will be holding a memorial service for Wittman at Bagram Air Base, the school also reported.

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

Another friend from school, Coast Guard Lt. Ryan W. Kilgo, said news of the loss is traveling globally through a Facebook account linking about 30 members of Wittman’s Lima Company, Class of ’07.

“Anything he wanted to do, he could accomplish it,” Kilgo remembered.

Reach Schuyler Kropf at 937-5551.