The two men knew each other because Dutschke used to work for Curtis' brother at an insurance company, under the direction of Curtis' ex-wife.
Curtis has said that while Dutschke worked for his brother, the two talked about collaborating on the publication of a book but later had a falling out.
He has accused Dutschke of stalking him online, a claim the latter has denied.
As for Dutschke, he told reporters last week that he didn't have a relationship with Curtis.
"He's just a little nutty," he said.
Yet while the last line of the letters to Obama, Wicker and Holland all contain Curtis's signature online catchphrase -- "I am KC and I approve this message" -- the newly unsealed affidavit ties them to Dutschke.
Among them, it states that marks on the paper for all those letters match those of paper found in Dutschke's home and trash.
Businessman, musician and convicted criminal
So who is James Everett Dutschke?
He's held several jobs, including at the insurance company and owner of his tae kwon do dojo. The Northeast Mississippi Daily Journal described him as a musician.
He was also an aspiring politician. He ran as a Republican against Democratic state Rep. Steve Holland, the son of Judge Sadie Holland, and lost. Judge Holland dismissed a civil lawsuit that Dutschke had filed against the witness who told investigators that Dutschke had talked about "poison."
Dutschke is also no stranger to law enforcement.
Last year, residents in his Tupelo neighborhood sought police help after, one neighbor says, Dutschke repeatedly exposed himself to young girls.
The case resulted in a conviction on indecent exposure charges and a 90-day jail sentence. He's appealed the conviction, according to the Daily Journal newspaper.
Then came another arrest on January 18, that is tied to the ricin case in two ways.
In that 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.
This arrest prompted him to close his tae kwon do dojo. After the arrest, he consented to the seizure of his laptop computer, a hard drive and several flash drives, the affidavit in the ricin case states.
Investigators searched these and found that on New Year's Eve 2012 someone had downloaded a publication, "Standard Operating Procedure for Ricin," about safely handling the toxin. They also found that another file, about a method for detecting ricin, had been downloaded about two hours later. But according to the affidavit, Dutschke insisted that he'd never researched anything about ricin and that he'd never even seen a castor bean.
Whether it was Dutschke or someone else, and whatever their motivation, the ricin-tainted letters could have done more than make headlines or scare people.
They could have killed.
If inhaled, injected or ingested, less than a pinpoint of ricin can kill a person within 36 to 48 hours due to the failure of the respiratory and circulatory systems. There is no known antidote.
In a seeming acknowledgment of these dangers, the FBI issued a statement Tuesday stating it had "immediately sealed off" Dutschke's former tae kwon do facility -- which is near an auto body shop and an ice cream parlor -- and contacted public health authorities in the interest of public safety.
"The FBI is now conducting further forensic examination for the purpose of identifying trace evidence, residues and signatures of production that could provide evidence to support the investigation," the agency said.