A man has been charged with sending an e-mail threatening presidential candidate Sen. John Kerry (search).

Robert V. Ruppert, 53, of Las Vegas was scheduled to be arraigned May 3. He was arrested April 13 and ordered detained pending trial.

A federal indictment released Tuesday charges Ruppert with making a threat to the candidate and states he "did knowingly and willfully threaten to kill, kidnap and inflict bodily harm upon Senator John Kerry."

The e-mail was sent to CNN newsman Wolf Blitzer and the White House, according to court documents.

Officials with the Secret Service would not release details of the e-mail.

"Suffice it to say that the threat contained in the e-mail left no doubt in the agents' minds," said a spokesman, Paul Masto. "There was no ambiguity. It was a direct threat."

Kerry, the presumptive Democratic presidential nominee and Massachusetts senator, was last in Las Vegas on Feb. 14 for the state caucus.