Atlanta (CNN) -- Federal agents charged four Georgia men they say are part of a fringe militia group with plotting to attack government officials with explosives and the biotoxin ricin, prosecutors in Atlanta announced Tuesday.
A government informant recorded the men discussing plans to manufacture ricin, a highly poisonous substance derived from castor beans, and attack Justice Department officials, federal judges and Internal Revenue Service agents, according to court papers released Tuesday afternoon.
Prosecutors said the public was never in imminent danger.
All four suspects were in custody and are scheduled to make their initial court appearances Wednesday in Gainesville, about 50 miles northeast of Atlanta, the U.S. attorney's office announced.
"When it comes time to saving the Constitution, that means some people gotta die," an arrest affidavit quotes one of the defendants, Frederick Thomas, as saying during one recorded conversation.
According to arrest affidavits filed in the case, 67-year-old Dan Roberts and Thomas, 73, agreed to buy a silencer, a bomb and parts to convert a semi-automatic rifle to a fully automatic machine gun from an undercover agent.
Meanwhile, 65-year-old Ray Adams and 68-year-old Samuel Crump worked to obtain castor beans and produce ricin, an FBI agent states in the documents.
"While many are focused on the threat posed by international violent extremists, this case demonstrates that we must also remain vigilant in protecting our country from citizens within our own borders who threaten our safety and security," U.S. Attorney Sally Quillian Yates said in a written statement announcing the arrests.
The affidavits don't identify the "known militia organization" of which FBI agents say the men are a part. But according to the documents, they talked about spreading ricin across several cities at once, including Washington, Atlanta, New Orleans and Jacksonville, Florida.
During an April meeting at his home, Thomas allegedly told participants he had a "bucket list" of politicians, government officials, corporate leaders and media figures he said should be targeted to "make the country right again."
"I could shoot ATF and IRS all day long. All the judges and the DOJ and the attorneys and prosecutors," the affidavit quotes Thomas as saying.
Crump allegedly said he wanted to make 10 pounds of ricin for distribution. "Dump that little (unintelligible) that's all you gotta do is lay it in the damn road, the cars are gonna spread it," the affidavit quotes him as saying.
According to one of the affidavits, Crump formerly worked for a contractor doing "maintenance type services" at the Centers for Disease Control and Prevention.
Crump also spoke of an even deadlier substance, "worse than anthrax," but the group would need financial backing to produce it, according to the affidavit.
The document states a castor bean provided to the informant by Adams and Crump tested positive for ricin.
The U.S. Agriculture Department verified Adams formerly worked at the Agriculture Research Service as a lab technician, an affidavit says.
According to another affidavit, Thomas allegedly said the group was ready to move forward with obtaining silencers from an active-duty member of the U.S. Army. In a phone call, he also said the four began physical training to prepare for their plans, the affidavit states.
Yates told CNN Atlanta affiliate WXIA that the investigation began earlier this year when an informant talked with the FBI about conversations he had overheard. The informant taped conversations with the four suspects and an undercover agent began talking with them, Yates said.
She said the defendants had taken "substantial steps" in the alleged plot.
"They had some of the (ricin) ingredients that were necessary but not all the ingredients," she said. "It's really important for the public to know and be assured that the FBI was on top of this and they were monitoring this every step of the way. "
Discussions on how to spread the ricin included driving down an interstate highway and allowing it come out the window, Yates told WXIA.
According to one affidavit, the confidential informant is on bond for pending felony state charges. An FBI polygrapher determined the individual "gave less than truthful responses concerning the activities of the militia group."
But, the affidavit states, the credibility of the informant has been demonstrated by the source's accurate recounting of the conversations the source recorded during meetings, "when compared to the audio and video recordings of the meetings and physical surveillance of those meetings conducted by law enforcement agents."
Adams, Crump and Roberts are from Toccoa, about 90 miles northeast of Atlanta, while Thomas is from nearby Cleveland, Georgia, prosecutors said.
CNN's Sara Pratley contributed to this report.