The U.S. Attorney General’s office arrested John P. Tomkins, a 42-year-old machinist from Dubuque, Iowa, on Wednesday, on suspicions he is the culprit who sent dud pipe bombs to the offices of American Century and Janus Capital with ominous messages signed “The Bishop,” the Associated Press reports. Tomkins, who was once a part-time U.S. Postal Service letter carrier, was on his way to work at a manufacturing facility. Federal agents began searching his home and a storage facility on Wednesday, and he was scheduled to appear in court in the afternoon.

Tomkins, who authorities believe intended to drive up stock prices, was charged with one count of mailing a threatening communication with intent to extort and one count of possession of an unregistered explosive device. The first charge carries up to 20 years in prison, the second, 10 years. Tomkins also faces a $500,000 fine.

Authorities have said that over the past year and a half, “The Bishop” mailed 16 threatening letters to financial institutions, saying they would face consequences if certain stocks didn’t move to $6.66.

Officials said that Tomkins’ handwriting matched the writing on some of the envelopes; he owns the same kind of car, a 1993 Chevrolet Lumina, as the man they were looking for; in December 2006, he purchased materials similar to those used in pipe bombs from a home improvement store; and trading records indicated he owned the stocks cited in the letters.

One of the letters read: “The way I see it, you owe it to us to make things right, or I will make your life as miserable as mine is.” Another read: “Time’s up. It is better to reign in hell than to serve in heaven.” Accompanying the two parcels containing pipe bombs was a letter that said, “Bang! You’re dead.”

“We take it quite seriously if anyone goes out and tries to mail threatening communications to people to affect the stock market,” said U.S. Attorney Patrick Fitzgerald.

State police, the Postal Inspection Service, the FBI Terrorism Task Force, the Bureau of Alcohol, Tobacco, Firearms and Explosives and the Securities and Exchange Commission also worked on the case.

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