(Newser) – Four US soldiers planned to overthrow the federal government and kill President Obama, the Press Association reports. The alleged plot, whose details remain scarce, emerged during a murder case against the soldiers. One of the four, Pfc. Michael Burnett, pleaded guilty to manslaughter and gang charges today in the deaths of an ex-soldier and his girlfriend, 17. The ex-soldier, Michael Roark, was killed because he was aware of the plot, Burnett said. The quartet had purchased $87,000 worth of firearms and explosives; they intended to attack Fort Stewart as well as locations in Georgia and Washington state, the AP reports. Click for our latest story on the plot. (Read more President Obama stories.)