An AWOL Muslim soldier who had been granted conscientious objector status earlier this year was arrested and bomb-making materials were found in his motel room near Fort Hood, the same Texas Army post where 13 people were killed in a 2009 shooting rampage blamed on an Army psychiatrist, an FBI spokesman said Thursday.

Killeen police arrested Pfc. Naser Abdo, 21, on Wednesday and agents found firearms and "items that could be identified as bomb-making components, including gunpowder," in his motel room, said FBI spokesman Erik Vasys.

A clerk at the gun store where the 2009 Fort Hood shootings suspect bought a pistol used in the attack told The Associated Press on Thursday that he alerted police after a man bought weapons and gunpowder there this week.

Greg Ebert said the man arrived at Guns Galore LLC by taxi Tuesday and bought 6 pounds of smokeless gunpowder, three boxes of shotgun ammunition and a magazine for a semi-automatic pistol, paying about $250. Ebert said he became concerned when the man asked questions indicating he didn't know much about the items.

"(We) felt uncomfortable with his overall demeanor and the fact he didn't know what the hell he was buying," Ebert said. "I thought it prudent to contact the local authorities, which I did."

Killeen police wouldn't immediately confirm Abdo was the buyer, but a U.S. official in Washington, speaking on condition of anonymity because he wasn't authorized to talk publicly about the case, confirms Abdo bought weapons at a Killeen gun shop.

Vasys said the FBI planned to charge Abdo with possessing bomb-making components later Thursday, at which time he would be transferred into federal custody. He said there was nothing to indicate Abdo was "working with others."