A soldier accused of having explosives in his carry-on luggage when he entered a Texas airport told investigators he used them in Afghanistan but didn't realize any were still in his bags, according to court documents.

Trey Scott Atwater of Hope Mills, N.C., was to be arraigned Tuesday in federal court, his first court appearance since his arrest Saturday. Authorities say the 30-year-old went through a security checkpoint at Midland International Airport with C-4, a powerful explosive.

He has been charged with trying to bring explosives onto an airplane, which carries a maximum 10-year federal prison sentence.

Atwater, based at Fort Bragg, N.C., told the FBI he is a demolitions expert who returned from his third deployment to Afghanistan in April, according to court documents. He said his Army special forces team always carried at least two blocks of C-4, but he didn't know any explosives were in his bag when he returned to the U.S.

He said he didn't see the explosives in the main compartment of the bag when he packed for his trip to Texas. The bag had been in his garage and hadn't been used since he returned from overseas, according to court documents.

Atwater and his family were headed back to North Carolina after visiting relatives when he was arrested in Midland, about 320 miles west of Dallas.

That was the second time on his trip that he was stopped by airport security. On Dec. 24, he was detained at the Fayetteville, N.C., airport when security agents found a military smoke grenade in his carry-on bag, according to court documents.

After the grenade was confiscated, Atwater was "admonished" and allowed to continue on the trip, according to documents. The Transportation Security Administration informed the FBI about that incident after Atwater's arrest.

"When I asked him about the December 24 Fayetteville incident after TSA informed me of it, Atwater acknowledged that it had occurred, but said he had forgotten to mention it to us during our initial interview," the FBI agent wrote in the affidavit filed in the case.

No one answered the door Tuesday at the home of Atwater's parents in a quiet middle-class neighborhood in Midland. An American flag between the two garage doors fluttered in the breeze.

A neighbor who lives two doors down, Pam Moore, 55, said she watched him grow up. She said he had been a "wonderful kid" who played high school football.

"We were real proud of him when he joined the military," Moore said. "I feel sorry that he got caught up in this. ... I just hope everything works out for him. I really do."