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ATLANTA (AP) — The suspected ringleader of what prosecutors said was a plot to attack government officials planned to plead guilty Tuesday to a charge in federal court, according to person familiar with the deal.

Frederick Thomas, 73, was set to enter the guilty plea at a hearing in Gainesville to a charge of conspiring to obtain an explosive, said the person, who requested anonymity ahead of the hearing.

Under the plea deal, Thomas could face up to five years in prison.

He is among four men arrested in early November after at least seven months of surveillance by an undercover informant who infiltrated their meetings at a Waffle House, homes and car rides. The dozens of hours of recordings the informant made are the linchpin to the government's case against the four.

In the tapes, the four allegedly boasted of a list of government officials who needed to be "taken out;" talked about scattering ricin from a car speeding down a highway past major U.S. cities; and scouted tax offices. One man said, "We'd have to blow the whole building like Timothy McVeigh," a reference to the man executed for bombing a federal building in Oklahoma City in 1995, killing 168 people.

The other three defendants were also set for hearing Tuesday. Ray Adams, 55, and Samuel Crump, 68, are charged with conspiring and attempting to make ricin. And Dan Roberts, 67, also faces charges of conspiring to obtain an explosive and he was set for a court hearing Tuesday. His attorney wouldn't immediately comment on whether he would plead to the charges.

Defense attorneys said the conversations were taken out of context and that the men were actually planning to unite various militia groups across Georgia to create a legitimate "governor's army" that would be at the state's disposal. But prosecutors say the men took a series of concrete steps toward carrying out a violent plot.

The four played very different roles in the plot, according to court testimony. Thomas was described as the "thought leader" who helped host meetings and recruit new members. He is accused of scouting the two federal buildings with the informant and leading the effort, along with Roberts, to get an illegal silencer and buy explosives from an undercover agent.

Prosecutors said those two men brought Crump and Adams into the mix after Roberts talked of obtaining a "silent killer" — the toxin ricin, which can be lethal in small doses. Crump had memorized the recipe for the poison, prosecutors said, and Adams had the know-how to make it as a former government lab technician.

In court hearings, defense attorneys claimed prosecutors were making too much of idle chatter from elderly men complaining at gatherings in local restaurants and at each other's homes. And they called on witnesses who testified that the three men were loyal to the government and often gave back to the community.