Carol Wallace last talked to her son, Marine Sgt. David W. Wallace, on Christmas morning, and he couldn’t have been more thankful for all the cards and letters that the people of the Shenango Valley sent him for the holidays.

“The joy in his voice reminded me of the young boy seeing all the presents under the Christmas tree,” Mrs. Wallace, of Sharpsville said in an e-mail to The Herald, which had published Wallace’s address through its Military Mail Call program.

Wallace was calling from Afghanistan. He sounded “wonderful” that day, Mrs. Wallace said Wednesday, leaving a joyous memory that took a bittersweet turn Tuesday, when Mrs. Wallace learned that her son had been killed.

Wallace was the first soldier from Mercer County to die in Afghanistan since the U.S. invaded to knock the Taliban from power.

Mrs. Wallace said her son died at 12:30 a.m. Eastern time, 10 a.m. Afghanistan time, in Helmand Province in the southern part of the country, in an improvised explosive device blast.

Wallace was on foot when the explosion occurred, but Mrs. Wallace said she did not have more details.

A spokesman for Camp Lejeune, North Carolina, where Wallace’s unit is based, said another member of his unit, Sgt. Trevor J. Johnson, 23, of Forsyth, Mont., also died. The spokesman said he had no details of the incident to release.

Wallace, 25, a Sharpsville native and 2002 graduate of Sharpsville High School, was a combat engineer with the 2nd Combat Engineer Battalion, 2nd Marine Division, II Marine Expeditionary Force.

His duties included identifying, removing and exploding IEDs, conducting searches, working on vehicles and construction projects, Mrs. Wallace said.

Wallace was involved in building an air base and helped construct a training village in Iraq.

“His main thing was to deal with IEDs,” Mrs. Wallace said.

Wallace left for Afghanistan Nov. 5. He served two tours in Iraq, from September 2004 to April 2005 and July 2007 to January 2008. He also served in Bangladesh, Dubai and other parts of the world with a Marine expeditionary force.

He entered the Marines on Sept. 23, 2002, enlisting under the buddy system with his friend, Mike Kulka.

Ron Haywood, another Buddy, said Wallace — better known as “Walleye” around town — had wanted to enlist for some time.

“He was talking about it since, I think, 10th grade, when the recruiters came in (to school),” Haywood said.