Mahmudiyah five years ago and to the attack by Hassan, who is facing death penalty court martial in the massacre two years ago at a Fort Hood deployment facility.
Abdo, a Muslim conscientious objector, has been accused by Killeen's police chief of preparing a terrorist attack that would have been directed at soldiers on and possibly off Fort Hood.
According to a criminal complaint filed Friday, Abdo, who was absent without leave from his post at Fort Campbell, Ky., admitted he planned to assemble two bombs in his Killeen hotel room using gunpowder and shrapnel packed into pressure cookers to detonate inside an unspecified restaurant frequented by soldiers at Fort Hood.
James Runkel, an FBI special agent assigned to Austin, filed the complaint alleging that Abdo possessed a firearm and a destructive device.
Runkel also stated Abdo "made statements to the arresting officer that he intended to conduct an attack against Killeen and Fort Hood" and that he "also indicated in response to questioning that there were explosives in the backpack and in his room."
FBI agents joined a search of Abdo's hotel room along with Killeen police and Fort Hood's criminal intelligence division. During the search, FBI Special Agent Bomb Technician Stephen Hauck, based in Austin, said that the components found by authorities "are those which can be used to construct a destructive device."
Abdo's initial court appearance on the weapons charge lasted about five minutes.
As U.S. Magistrate Judge Jeffrey Manske came into the courtroom with a bailiff calling "All rise," Abdo sat.
Four U.S. marshals came to his side, took him by the arms and made him stand before the judge.
Manske then proceeded to question him about his educational status. Abdo, who is from Garland, told the judge that he had graduated from high school and had one year of college.
Manske then asked if he was unable to understand why he was in the courtroom and if he was under the influence of any drugs or alcohol. Abdo replied "no." The judge read him his rights as Abdo stood before a lectern with two U.S. marshals at his side.
When he was asked by the judge if he understood his right to remain silent, Abdo replied, "I sure do."
Abdo faces a maximum sentence of 10 years in prison, a $10,000 fine and three years of supervised release.
Abdo, who is being held without bail because of his AWOL status, was remanded into the custody of the U.S. Marshals Service, where he will remain until his trial.
The judge set another hearing for 2 p.m. Thursday in Waco and closed the hearing.
A group of marshals surrounded Abdo as the judge rose from his bench and left.
Abdo, wearing a short military haircut, stood, startling everyone as he called out his defiant statement in a strong voice. Then he was gone.