In a statement to reporters outside the courtroom he confessed to making "some terrible mistakes".
The authorities said Mr. Helder had confessed to making 24 pipe bombs.
Mr. Helder confessed to making the bombs and was taken from Reno, Nev., to Iowa to face felony charges.
Last month, a 12-year-old boy confessed to making calls that drew the authorities to the home of the actor Ashton Kutcher and to Mr. Bieber.
As it turned out, a Queens bartender confessed to making the call that somehow got through the Coliseum switchboard to the visiting coach's office.
Some horseplayers confessed to making the drive to Connecticut and the Mohegan Sun Casino to bet races that ran in other parts of the country over the weekend.
His resignation letter, in which he confessed to making up stories during his two years at the tabloid, received widespread attention after it was disseminated via Twitter.
A freshman at Georgia Tech confessed to making bombs that injured a janitor and prompted the evacuation of two dormitories on Monday, the police said.
He & other former Lockheed officials have maintained that the company, one of more than 300 American corporations that have confessed to making such payments in foreign countries, was serving as a "scapegoat".
But Rowling has confessed to making her mark on the room within which she wrote the last pages for the final instalment of the Harry Potter series to celebrate its completion.
