Dutschke said he once met Wicker.
Suspect No. 1
The letters 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.
Each letter had a Memphis, Tennessee, postmark and no return address.
The very next day, authorities arrested Curtis.
His attorney, Christi McCoy, said he'd been framed by someone who used several phrases Curtis likes to use on social media.
The FBI said the letters tested positive for ricin, a toxin derived from castor beans that has no known antidote.
The very next week, authorities dropped the charges against Curtis after they said they had new information.
"I think now, how many people are thrown in jail because of circumstantial evidence and someone can frame you that easily," he told CNN last week after being cleared.
Suspect No. 2
The feds then turned their attention to Dutschke.
Agents searched his residence and former martial arts studio. Dutschke told CNN affiliate WMC-TV that he agreed to the FBI search "to help clear my name."
"I had absolutely nothing to do with those letters," he said.
Early Saturday, he was arrested without incident at home. He was charged with possession and use of a biological agent as a weapon in connection with the letters.
This isn't his only brush with the law.
Dutschke faces molestation charges in an unrelated case.
According to a grand jury indictment handed up this month and obtained by CNN, Dutschke is accused of molesting three girls under the age of 16. He has repeatedly denied the charges in interviews with local media and pleaded not guilty in court this month.
Dutschke closed his tae kwon do studio after the allegations were made public.
Dutschke was previously convicted on indecent exposure charges in another case and sentenced to 90 days in jail.
A song in his heart
As for Curtis, he told CNN he's "just glad it's over."
When he learned Dutschke had been arrested, he took a deep breath and felt like "a weight had been taken off."