CHICAGO (CBS) — A jury has convicted an Iowa man of sending threatening letters and dud pipe bombs to investment advisers in the Chicago area.

John Tomkins, 47, of Iowa, was convicted on all counts by the jury after just hours of deliberation. The conviction could mean more than 200 years in prison.

Tomkins represented himself at the two-week trial before U.S. District Judge Robert Dow, and often referred to himself in the third person.

In closing arguments Thursday, Tompkins even admitted to sending packages to the suburban investment firms. But he insisted he knew the pipe bombs were duds and said he designed them so they would never explode.

“He mailed threatening letters,” said Tomkins, who was referring to himself in the third person at the time. “Hold him accountable for what he did.”

He told jurors in closing arguments that he is far more than just a rural relief mail carrier. He is a skilled machinist, union secretary-treasurer, stock car driver and builder, and attendant father.

Prosecutors said Tomkins wanted investment houses to raise the price of stock he owned in two technology firms.

Prosecutors allege Tomkins sent letters from 2005 until 2007 that threatened to kill those who received them, their families and neighbors unless they took action to raise the stock prices of 3COM Corp. and Navarre Corp., in which Tomkins had invested. They allege he mailed the pipe bombs from a suburban Chicago post office in 2007.

Tomkins, who Assistant U.S. Attorney Patrick Pope said identified himself in some of the letters as “The Bishop,” allegedly taunted the people who received them.

“Bang, you’re dead,” Pope quoted from one of the letters that accompanied a pipe bomb during his opening argument. “The only reason you’re alive is that I did not attach one wire.”

Prosecutors said the pipe bombs were real and would have detonated had all the wires been attached. Pope said the letters included a threat that the advisers better drive up the stock prices by a deadline he gave them or he would send more bombs, making sure to “connect all the wires,” before ending with the words “Tick, tock” or “Time’s up.”

(TM and © Copyright 2012 CBS Radio Inc. and its relevant subsidiaries. CBS Radio and EYE Logo TM and Copyright 2012 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed. The Associated Press contributed to this report.)

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