A Mississippi man charged with mailing letters with suspected ricin to national leaders believed he had uncovered a conspiracy to sell human body parts on the black market, and on Thursday his attorney said he was surprised by his arrest and maintains he is innocent.

Paul Kevin Curtis, 45, wore shackles and a Johnny Cash T-shirt Thursday in a federal courtroom. His handcuffs were taken off for the brief hearing, and he said little. He faces two charges on accusations of threatening President Barack Obama and others. If convicted, he could face up to 15 years in prison.

He did not enter a plea on the two charges. The judge said a preliminary hearing and a detention hearing are scheduled for 3 p.m. today.

Attorney Christi R. McCoy said Curtis “maintains 100 percent that he did not do this.”

McCoy said she has not yet decided whether to seek a hearing to determine whether Curtis is mentally competent to stand trial.

Curtis, who was arrested Wednesday at his home in Corinth, near the Tennessee state line, was being held in the Lafayette County jail in Oxford, Miss.

An FBI affidavit says Curtis sent three letters with suspected ricin to Obama, U.S. Sen. Roger Wicker and Lee County, Miss., Justice Court Judge Sadie Holland. The letters read:

“No one wanted to listen to me before. There are still ‘Missing Pieces.’ Maybe I have your attention now even if that means someone must die. This must stop. To see a wrong and not expose it, is to become a silent partner to its continuance. I am KC and I approve this message.”

The affidavit says Curtis had sent letters to Wicker’s office several times before with the message, “this is Kevin Curtis and I approve this message.”

Holland received a threatening letter April 10 with a substance that has been sent to a lab for testing. The letter was signed “K.C.”

In several letters to Wicker and other officials, Curtis said he was writing a novel about black market body parts called “Missing Pieces.”

Curtis also had posted language similar to the letters on his Facebook page, the affidavit says.

The documents indicate Curtis had been distrustful of the government for years. In 2007, Curtis’ ex-wife called police in Booneville, Miss., to report that her husband was extremely delusional, anti-government and felt the government was spying on him with drones.

Curtis had been living in Corinth, a city of about 14,000 in extreme northeastern Mississippi, since December, but local police had not had any contact with him before his arrest, Corinth Police Department Capt. Ralph Dance said Thursday.

Ricky Curtis, who said he was Kevin Curtis’ cousin, described his cousin as a “super entertainer” who impersonated Elvis and numerous other singers.

Wicker said Thursday in Washington that he had met Curtis when he was working as Elvis at a party Wicker and his wife helped throw for an engaged couple.

Wicker called him “quite entertaining” but said: “My impression is that since that time he’s had mental issues and perhaps is not as stable as he was back then.”

Wicker’s spokesman, Ryan Annison, said the party occurred about 10 years ago.

Police maintained a perimeter Thursday around Curtis’ home. Four men who appeared to be investigators were in the neighborhood to speak to neighbors. There didn’t appear to be any hazardous-material crews, and no neighbors were evacuated.

The material discovered in a letter to Wicker has been confirmed through field testing and laboratory testing to contain ricin, Senate Sergeant-at-Arms Terrance Gainer said Thursday. The FBI has not yet reported the results of its own testing of materials sent to Wicker and to President Barack Obama.