A man accused of mailing letters tainted with ricin to U.S. President Barack Obama and other officials believed he had uncovered a conspiracy to sell human body parts on the black market and claimed "various parties within the government" were trying to ruin his reputation.

Paul Kevin Curtis, 45, is charged with threatening Obama and others, according to a Thursday news release from the U.S. Department of Justice. He appeared in federal court on the two charges and if convicted could face up to 15 years in prison. He did not enter a plea on the two charges. Another hearing is Friday.

Curtis was surprised by his arrest, his attorney said after the hearing.

Curtis "maintains 100 per cent that he did not do this," attorney Christi R. McCoy said. She added that she knows him and his family and that it is hard for her to believe the charges against him.

She said she had not yet decided whether to seek a hearing to determine if Curtis is mentally competent to stand trial. Another attorney working with Curtis' family said he had a history of mental illness.

An FBI affidavit released Thursday said Curtis sent three letters with suspected ricin to Obama, U.S. Sen. Roger Wicker of Mississippi and a Mississippi judge. 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 FBI said there was no indication of a connection between the letters and the Monday bombing in Boston that killed three people and injured more than 170. The letters to Obama and Wicker were postmarked April 8, before the marathon.

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." Such language is typically used by candidates at the end of campaign ads.

Novel about black market body parts

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 to report that her husband was extremely delusional, anti-government and felt the government was spying on him with drones.

Wicker said Thursday that he had met Curtis when he was working as an Elvis impersonator at a party about a decade ago. 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."

Curtis was arrested Wednesday at his home. Local police had not had any contact with him prior to his arrest, Corinth Police Department Capt. Ralph Dance told The Associated Press on Thursday.

The FBI said Thursday that laboratory tests have confirmed the presence of ricin in the letters.

Ricin is derived from the castor plant that makes castor oil. There is no antidote, and it's deadliest when inhaled. The material sent to Wicker was not weaponized, Gainer said.

Family shocked

Ricky Curtis, who said he was Kevin Curtis' cousin, said the family was shocked. He described his cousin as a "super entertainer" who impersonated Elvis and numerous other singers.

"I don't think anybody had a clue that this kind of stuff was weighing on his mind," Ricky Curtis said in a telephone interview.

Ricky Curtis said his cousin had written about problems he had with a cleaning business and that he felt the government had not treated him well, but he said nobody in the family would have expected this.

A MySpace page for a cleaning company called The Cleaning Crew confirms that they "do windows" and has profile photo of "Kevin Curtis, Master of Impressions." A YouTube channel under the name of Kevin Curtis has dozens of videos of him performing as different famous musicians, including Elvis Presley, Buddy Holly and Kid Rock.

Multiple online posts on various websites under the name Kevin Curtis refer to the conspiracy he claimed to uncover when working at a local hospital from 1998 to 2000. The author wrote that the conspiracy began when he "discovered a refrigerator full of dismembered body parts & organs wrapped in plastic in the morgue of the largest non-metropolitan health care organization in the United States of America."

Curtis wrote that he was trying to "expose various parties within the government, FBI, police departments" for what he believed was "a conspiracy to ruin my reputation in the community as well as an ongoing effort to break down the foundation I worked more than 20 years to build in the country music scene."

In one post, Curtis said he sent letters to Wicker and other politicians.

"I never heard a word from anyone. I even ran into Roger Wicker several different times while performing at special banquets and fundraisers in northeast, Mississippi but he seemed very nervous while speaking with me and would make a fast exit to the door when I engaged in conversation..."

Attorney Jim Waide said he was working with Curtis' family to put together a statement. Waide said the family told him Curtis has been diagnosed as bipolar and was put on medication about three years ago. "It's been a real problem to keep him on his medication," Waide said in a phone interview.

"He has a long history of mental illness," Waide said. "When he is on his medication, he is terrific, he's nice, he's functional. When he's off his medication, that's when there's a problem."