OXFORD, Miss. — The Mississippi man charged with mailing letters with suspected ricin to national leaders was surprised by his arrest and maintains he is innocent, his attorney said today after his first appearance.

Paul Kevin Curtis, 45, wore shackles and a Johnny Cash T-shirt in the 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.

He nodded his head and said, “Yes, ma’am” when the judge asked whether he understood the charges and possible penalties

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. Friday.

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

“I know Kevin, I know his family,” she said. “This is a huge shock.”

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

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

An FBI affidavit says Curtis sent three letters with suspected ricin to President Barack Obama, U.S. Sen. Roger Wicker 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.”