This undated photo obtained from the facebook page of Paul Kevin Curtis, shows, according to neighbors, Paul Kevin Curtis, 45.

CORINTH, Miss. - A Mississippi man accused of mailing letters with suspected ricin to national leaders 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 President Barack Obama and others, according to a news release today from the U.S. Department of Justice. He is scheduled to appear in federal court on the two charges later today, and if convicted could face up to 15 years in prison

An affidavit says the letters sent to Obama, U.S. Sen. Roger Wicker and a judge in Mississippi told the recipients: "Maybe I have your attention now even if that means someone must die."

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

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 prior to his arrest, Corinth Police Department Capt. Ralph Dance told The Associated Press today. Dance said the department aided the FBI during the arrest and that Curtis did not resist being taken into custody. Since Curtis arrived in the town, he had been living in "government housing," Dance said. He did not elaborate.

Police maintained a perimeter today around Curtis' home, and federal investigators were expected to search the house later in the morning, said local officers on the scene who declined to be identified. 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, said Senate Sergeant-at-Arms Terrance Gainer. The FBI has not yet reported the results of its own testing of materials sent to Wicker and to President Barack Obama.

"Our field tests indicate it was ricin. Our lab tests confirm it was ricin. So I don't get why others are continuing to use equivocal words about this," Gainer said.

Preliminary field tests can often show false positives for ricin. 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.

An FBI intelligence bulletin obtained by The Associated Press said the two letters were postmarked Memphis, Tenn.

Both letters said: "To see a wrong and not expose it, is to become a silent partner to its continuance." Both were signed, "I am KC and I approve this message."

The letters had Washington on edge in the days after the Boston Marathon bombing. As authorities scurried to investigate three questionable packages discovered in Senate office buildings Wednesday, reports of suspicious items also came in from at least three senators' offices in their home states. The items were found to be harmless.

In addition, a Mississippi state lawmaker, Democratic Rep. Steve Holland of Plantersville, said Wednesday night that his 80-year-old mother, Lee County Justice Court Judge Sadie Holland, received a threatening letter last week with a substance that has been sent to a lab for testing. He said this letter was also signed "K.C."

"She opened it herself" on April 11 and told Holland about it three days later, Holland said.

He said she had not been to the doctor, but he planned to take her Thursday.

"She's fine," Holland said. "She's had no symptoms."

Curtis' neighbors, who said he did not seem violent, were concerned about their safety Thursday and worried by the idea that someone was making poison in a house that sits so close to their bedrooms and front yards. The one-story, single-family home is similar to the others in the neighborhood - red brick with white trim.

A church, and a community center with an outdoor children's play area, are just steps from Curtis' house. The home also is near an area with several mailboxes for the community. But neighbors said they rarely saw him retrieve mail and didn't speak with him much.

"He was quiet. He pretty much stayed to himself," said neighbor Lacey Ross, 29.

Next-door neighbor Kayla Latch, 18, lives with her mother and her two brothers and said they were worried that toxic chemicals could be released when investigators enter the home.

"I'm afraid they might open it up and it (poison) might go into the air and hurt someone," Latch said.

Latch said Curtis lived with a woman and a teenage boy when he first moved in, but they appeared to have moved out.

Matthew Latch, Kayla's brother, said he would sometimes hear Curtis playing his guitar outside the house late at night.

The Latches said he sometimes would be out all night, then stay home all day and not come out again until nightfall. He also would be away from the home over an entire weekend, they said.

Kayla Latch said she slept in the living room Wednesday night.

"I'm still a little scared because my room is right next to his house," Latch said. "I didn't even sleep in my bed."

Latch's mother, Melissa Strickland, two men who identified themselves as being with the FBI came to her house today and asked about the man next door. She said they never identified Curtis by name.

"They asked me if I saw a lot of people coming and going from his house," she said. "I told them, "No."

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

"We're all in shock. 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. He said the writings were titled, "Missing Pieces."

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.

"As far as him being anti-government, I'm not going to say that, but he had some issues with some stuff that happened with his cleaning business," the cousin said.

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 the conspiracy that 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..."

He signed off: "This is Kevin Curtis & 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.

Obama's press secretary, Jay Carney, said mail sent to the White House is screened at a remote site for the safety of the recipients and the general public. He declined to comment on the significance of the preliminary ricin result, referring questions to the FBI.

At a House hearing, Postmaster General Patrick Donahoe noted there had been ricin alerts since the notorious 2001 anthrax mailings and procedures are in place to protect postal employees and help track down culprits.

"Over the course of years we've had some situations where there have been ricin scares," Donahoe said. "Until this date, there's never been any actually proved that have gone through the system."