Arlington National Cemetery marked a grim milestone today with the burial of its 400th casualty of the war in Iraq.

Navy Chief Petty Officer Mark Carter, 27, of Fallbrook, Calif., was laid to rest the week before Christmas in a ceremony closed to press coverage. He was killed Dec. 11 during combat operations in Iraq.

Four hundred families have now buried their loved ones at Arlington since the cemetery's first Iraq casualty, Army Capt. Russell Rippetoe, was interred on April 10, 2003. Sixty casualties of the war in Afghanistan are also buried at Arlington.

From an early age, Carter's sights were set on joining the Navy's elite Sea Air Land commandos, or SEALs.

"That's all he ever wanted to do," a friend told the North County Times. "His goal in life was to be a Navy SEAL."

Carter hung SEAL posters on his walls and enjoyed such extreme sports as skateboarding, paint ball, and rock climbing.

"He was a bit of a thrill-seeker," a family friend told the Virginian-Pilot.

Carter skipped college and enlisted in the Navy in 1998. He entered the SEAL program the following year. A muscular 5-foot-5 ("just a little fireplug"), he proved his mettle in Iraq and Afghanistan, earning two Bronze Stars for combat valor.

"He was the type of kid you wanted on your side if you were ever in a fight," the family friend told KNSD.

The Navy would say only that Carter died "as a result of enemy action while conducting combat operations in Iraq." He is survived by his parents, three brothers, and four sisters.