Federal agents arrested a 42-year-old former postal worker in Dubuque, Iowa, this morning who they say mailed threatening letters and unarmed bombs to Midwest investment firms, calling himself "The Bishop." Authorities told ABC News John Patrick Tomkins was taken into custody at first light this morning at his home in Dubuque. "The Bishop" was the name used by the person who had been sending threatening letters and unarmed pipe bombs since 2005, according to homeland security officials. Two bombs were sent to investment firms in Kansas City and Chicago. Read the Criminal Complaint Against John Patrick Tomkins. Investigators say they were led to Tomkins through handwriting analysis and the purchase of bomb-making materials with a credit card they say was linked to him. "The Bishop" also mailed a picture that had a car door in the background, identified as belonging to a 1990 to 1995 Chevy Lumina. Tompkins had been seen driving a 1993 Chevy Lumina, according to law enforcement officials. Officials had sent out national alerts about "The Bishop," comparing him to the Unabomber, whose mail bombs killed three people and terrorized the country into the early 1990′s. No one was injured by any of "The Bishop’s" packages. "The Bishop’s" first letters, in 2005, demanded that targeted companies take steps to move certain stocks to a specific price, often $6.66. Officials said the unarmed pipe bomb sent by "The Bishop" to Perkins, Wolf, McDonnell & Co. of Chicago, included a letter that said, "The only reason you’re alive is I didn’t attach one wire. There’s nothing the police or anybody can do, so don’t contact them."