MIDLAND, Texas (AP) — A soldier charged with trying to bring explosives on an airplane in Texas told investigators he used them in Afghanistan but didn’t realize any were in a bag he brought back to the U.S. and apparently carried on a flight from North Carolina to Texas.

Trey Scott Atwater (pictured), of Hope Mills, N.C., was arrested Saturday while trying to go through security at an airport in Texas where he was planning to fly back home. Authorities say the 30-year-old had a carry-on bag containing C4, a powerful explosive used in Iraq and Afghanistan to blow the hinges off doors or destroy unexploded ordinance.

According to court documents, Atwater told the FBI he is a demolitions expert who returned from his third deployment to Afghanistan in April. He said his Army special forces team always carried at least two blocks of C4, but he didn’t know any explosives were in his bag when he returned to his post at Fort Bragg, N.C.

He said the bag had been in his garage since then and he didn’t see any explosives in the main compartment when he packed for his trip to Texas.

Atwater was detained at the Fayetteville, N.C., airport on Dec. 24 when security agents found a military smoke grenade in his carry-on bag.