(CNN) -- A 41-year-old Mississippi man pleaded guilty Friday in federal court months after being accused of developing ricin and sending the dangerous substance in letters to President Barack Obama and others, the U.S. Department of Justice announced.
According to a plea agreement, James Everett Dutschke is expected to be sentenced to 25 years in prison. The Tupelo resident will be sentenced in by U.S. District Judge Sharion Aycock in about 60 days.
CNN first learned of Dutschke's plea via Twitter.
Dutschke was arrested on April 27, 2013, and charged with possession and use of a biological agent as a weapon.
The agreement wraps up a bizarre case that began when federal investigators first arrested another man -- an Elvis impersonator named Paul Kevin Curtis -- for allegedly sending letters containing ricin to Obama, Sen. Roger Wicker, R-Mississippi; and Sadie Holland, a judge in Lee County.
Ricin is a deadly toxin derived from castor beans that has no known antidote.
The letters to Wicker and Obama were stopped at a government mail-screening facility after initial tests indicated the presence of the deadly poison ricin. The one sent to Holland did not cause any illness.
Even so, the case -- which came on the heels of the Boston Marathon bombings -- spurred anxieties around the country about such biological attacks. In a way, it recalls the days after the September 11, 2001, terrorist attacks when U.S. senators and journalists were sent anthrax-laced letters.
Authorities cleared Curtis after his attorney, Christi McCoy, told authorities that she believed her client was framed, possibly by Dutschke.
In fact, FBI agents were searching Dutschke's home and the studio where he practiced martial arts as Curtis walked out of jail. At the time, Dutschke told CNN affiliate WMC-TV that he was cooperating with the FBI and had nothing to do with the letters.
"I had absolutely nothing to do with those letters," he said at the time.
Friday's plea shows that was not true.
The Justice Department said, in its press release Friday, that Dutschke concocted and carried out the elaborate ploy -- including buying castor beans or seeds to make ricin via eBay -- then making the toxin and enclosing it in the three letters.
Each of the letters had a Memphis, Tennessee, postmark and no return address. They read, in part: "To see a wrong and not expose it, is to become a silent partner to its continuance."
They were signed "I am KC and I approve this message," a source told CNN.
CNN's Chelsea J. Carter contributed to this report.