Killeen, Texas (CNN) -- The U.S. Army private who authorities say admitted to planning to bomb a restaurant popular with soldiers from Fort Hood is to be held without bond, a federal magistrate ordered Friday.
Pfc. Naser Jason Abdo was formally charged with possession of an unregistered destructive device. Additional charges are likely, said Daryl Fields, a spokesman for the U.S. attorney's office in San Antonio, Texas.
Abdo, who refused to stand when Judge Jeffrey C. Manske entered the courtroom, shouted an apparent reference to the 2006 rape of an Iraqi girl by U.S. soldiers and the 2009 shooting spree at Fort Hood by Army Maj. Nidal Hasan before being hustled out of the courtroom by marshals.
Abdo, a Muslim American soldier who had been granted conscientious objector status before going AWOL, was being held Friday in federal custody at an undisclosed location.
According to the criminal complaint unsealed after his appearance Friday, Abdo admitted he planned to turn two pressure cookers found in his Killeen hotel room into gunpowder- and shrapnel-filled bombs to detonate inside an unnamed restaurant popular with soldiers from Fort Hood.
Among other things, police and FBI investigators who searched the room found six bottles of gunpowder, shotgun shells and pellets and ammunition cartridges.
Police who arrested him found wire, a handgun, ammunition and an article titled, "Make a bomb in the kitchen of your Mom" in the backpack he was carrying, according to the complaint. The backpack also contained a notebook with a hand-written list for many of the components police recovered.
The public defender appointed to represent Abdo, attorney Keith Dorsett of Waco, did not immediately respond to e-mails and telephone messages seeking comment.
Killeen police arrested Abdo, 21, on Wednesday after a gun store employee tipped them that Abdo's behavior had raised red flags when he purchased six pounds of smokeless gunpowder and other supplies.
The tip came from Greg Ebert, a retired police officer who works at the Guns Galore gun store. He said the young man appeared suspicious as soon as he pulled up in a taxi cab.
"How many people go shopping at gun stores in a taxi cab?" Ebert asked. He described Abdo as being guarded and asking odd questions.
Abdo browsed for about 20 minutes, Ebert said, choosing six pounds of gunpowder, shotgun ammunition and a magazine for a semiautomatic handgun. He asked Ebert what smokeless gunpowder was before finishing the purchase.
"Well, hello! Why are you buying this if you don't know what it's for?" Ebert said later. "That is a red flag for me. He should know. Why is he buying that much?"
Ebert said he called police after discussing the transaction at length with the owner of the store, which is the same place where Hasan bought supplies for his shooting spree.
Abdo joined the infantry in 2009 and was assigned to Company E of the 101st Airborne Division's 1st Brigade Combat Team when he refused to deploy to Afghanistan on religious grounds.
The Army approved his request to be discharged as a conscientious objector. But on May 13, he was charged with possession of child pornography on his computer, according to the statement.
After a June 15 hearing, at which Abdo was recommended for court-martial, he went AWOL.
In media interviews last year, Abdo talked about seeking conscientious objector status, saying he felt compelled to remain true to his faith.
"We have two things that I believe make us American, and that's freedom of religion and freedom of choice," he said.
When he signed up for the military, Abdo said, he had not thought that his religious beliefs would be an issue. "I was under the impression that I could serve both the U.S. Army and my God simultaneously," he said.
But as his deployment neared, he began to rethink things and eventually worked up the courage to approach his unit and tell them how he felt, he said.
"Islam is a much more peaceful and tolerant religion than it is an aggressive religion," he said. "I don't believe that Islam allows me to operate in any kind of warfare at all, including the U.S. military and any war it partakes in. I believe that our first duty as a Muslim is to serve God."
In court Friday, Abdo mentioned "Iraq 2006," an apparent reference to an incident in which U.S. Army soldiers were accused of killing three members of an Iraqi family, including a 6-year-old girl, and raping the family's 14-year-old girl before also killing her and setting the bodies on fire in an attempt to cover up the killings.
Four soldiers were convicted and imprisoned for their roles in the shootings, rape and subsequent cover-up.
After Abdo's arrest, Texas Gov. Rick Perry issued a statement calling it "a sobering reminder of the importance of remaining vigilant in the ongoing efforts to protect our communities from those that would do us harm."
Rep. John Carter, R-Texas, the House Army Caucus chairman, praised the gun-shop employee who tipped police to Abdo, as well as the police themselves, for interrupting what could have been a deadly plot.
"Thanks to quick action by a Texas gun dealer in alerting local police to a suspicious character, and a prompt and vigorous response by the Killeen Police Department, we may well have averted a repeat of the tragic 2009 radical Islamic terror attack on our nation's largest military installation," he said.
"We now have an example of what works to prevent these type attacks, and as the coming days reveal more details about this attempt, we can determine better ways to thwart similar efforts in the future," Carter said.
In addition to being the site of the Fort Hood shootings, Killeen is also where, in 1991, George Hennard crashed his pickup into a Luby's cafeteria, fatally shot 23 people and wounded another 20 before killing himself.
"We've been through a lot in this community," Killeen Police Chief Dennis Baldwin said. "But I can tell you that's when the character of the community is more obvious."
CNN's Tracy Sabo, Barbara Starr, Marylynn Ryan and Carol Cratty contributed to this report.