SAVANNAH, Ga. — Army Pvt. Isaac Aguigui, of Cashmere, held the Army's lowest rank, served in the military less than two years and never saw combat. Yet Georgia prosecutors say the 21-year-old soldier from Chelan County, commanded enough authority to form an anti-government militia within the U.S. military with soldiers of greater rank and experience following his orders — including an order to commit murder.

That an untested soldier might possess such power adds another odd twist to an unfolding legal case full of stunning allegations.

Prosecutors in rural southeast Georgia said in court this week that Aguigui and three fellow soldiers at Fort Stewart killed a former Army comrade, also from Washington state, and his girlfriend last December. Their motive, prosecutors said, was to protect a secret plot to assassinate the president and overthrow the U.S. government — and along the way to bomb a park fountain in nearby Savannah, poison apple orchards in Washington and take over the Army post where they were stationed. Authorities say the group stockpiled guns and bomb components.

Federal authorities have not said publicly whether they considered Aguigui and his associates a serious threat.

Aguigui was due back in court Thursday along with two fellow soldiers for arraignment on charges including malice murder, felony murder and illegal gang activity in the Dec. 4 slayings of former Army Pvt. Michael Roark and his 17-year-old girlfriend, Tiffany York. Roark was born in Kirkland and went to high school in Marysville. Defense attorneys for the three men did not return messages from The Associated Press.

The three are being prosecuted in Georgia's Atlantic Judicial Circuit. The Army filed murder charges against them in March, but dropped them Aug. 15.

A fourth Fort Stewart soldier pleaded guilty to reduced charges Tuesday and told a judge Aguigui ordered two older, more experienced soldiers to commit the killings.

Pfc. Michael Burnett, the soldier who cut the plea deal, told the judge that Sgt. Anthony Peden, a 26-year-old veteran of two tours in Afghanistan whose Army record lists 16 medals and commendations, shot the teenage girl twice at Aguigui's command. Burnett also testified Pvt. Christopher Salmon, 26, with one Iraq tour, put Roark on his knees and shot him in the head.

Whatever the young private lacked in rank and combat experience, he had something else: roughly $500,000. Pauley said he received the life insurance and benefit payments after his wife, Army Sgt. Deirdre Aguigui, died.

Prosecutors say Aguigui bought $87,000 worth of semi-automatic assault rifles, other guns and bomb-making materials. Aguigui would give Roark money to buy weapons for him, the slain soldier's father said.

"They were using Michael and other kids as straw buyers, giving them money to go buy guns," said Brett Roark, citing conversations with prosecutors. "He wasn't a member of the gang."

The slain girl's older brother said he knew something was wrong when Roark started giving her cash and expensive clothes, sunglasses and other gifts.

"An E-1 (private) in the military does not make big money like he was giving Tiffany," said Nicholas Lee York, who said his sister told him that she and Roark had a "rich friend."

"I heard about their friend Isaac Aguigui and how he would give them a bunch of money."

Regina Ross-Schmid, an Army spouse at Fort Stewart and friend of Aguigui's wife, said soldiers who served with the woman were never given an explanation of her death.

"When we first were told she had died, what was said was she laid down to take a nap and when Isaac went to wake her up, he couldn't wake her up," Ross-Schmid said. Ross-Schmid said she met Aguigui for the first time at a memorial service for his wife on Fort Stewart.

"Everybody who spoke at the memorial was trying to choke back tears, these big strong Army men, and he's not showing any emotion at all," she said. "At the time I said, maybe he's in shock. I don't know. I can't explain it. It just seemed odd."

Associated Press writer Kate Brumback in Atlanta contributed.