But when he was discovered Wednesday, Abdo was apparently in the final planning stages of a deadly attack. He was caught in part because a wary local gun store owner called police after Abdo visited the store to buy ammunition and gunpowder. He was acting "suspicious," Guns Galore owner Greg Ebert told ABC News.
"There was clearly something wrong with him," Ebert said. "We made a decision to call the police and fortunately it worked out."
After his arrest, Abdo admitted he planned to plant two bombs at a local restaurant frequented by Fort Hood soldiers and hoped to gun down any survivors of the dual blast, according to law enforcement documents obtained by ABC News.
According to the documents, military officials believe the incident "was likely isolated to the Fort Hood area and the suspect in custody, and that arrest of the suspect has mitigated any further threats related to this incident."
Abdo's former lawyer, James M. Branum, declined to comment for an ABC News report except to say Thursday he hasn't spoken with his client "in a long time."
ABC News' Sarah Netter, Luis Martinez and Lee Ferran contributed to this report.