By HEATHER HOLLINGSWORTH Associated Press Writer KANSAS CITY, Mo. (AP) -- He calls himself "The Bishop." Exactly why is just one of the many mysteries surrounding the increasingly menacing figure. The man _ and investigators believe they are dealing with a man _ is suspected of sending at least a half-dozen threatening letters to financial institutions over the past 18 months and mailing two dud pipe bombs that arrived a day apart in Kansas City and Chicago in January. In his letters, The Bishop has demanded that financial companies move the prices of certain stocks to certain levels, often $6.66 _ an apparent reference to the Antichrist, said corporate counterterrorism expert Fred Burton. Burton, whose security firm has been hired by financial companies to find The Bishop, said the pipe bombs were assembled with crucial components deliberately left out, in what was probably a warning. Next time, Burton said, the bombs could be real. But catching The Bishop and figuring out exactly what his grudge is could require help from the public, Burton said, noting that it was Unabomber Ted Kaczynski's own brother who turned him in and ended the 17-year series of bombings that killed three people and injured 23. David Kaczynski got suspicious after reading the Unabomber's anti- technology manifesto, published in the newspapers. The Bishop, like the Unabomber, is probably mentally ill, highly intelligent and a loner, said Burton, vice president of counterterrorism for Stratfor, an Austin, Texas, security and intelligence firm. Postal inspectors are offering a reward of up to $100,000 for information. The investigation also includes the FBI, the Bureau of Alcohol, Tobacco, Firearms and Explosives, and local law enforcement agencies. Spokesmen for the FBI and the Postal Inspection Service would not comment in any detail on the investigation. Burton said some of Stratfor's financial clients asked his firm to investigate in 2005 after The Bishop began sending threatening letters from various Midwestern states, including Wisconsin and Iowa. Burton, who said he has many sources within law enforcement, wrote in a weekly terrorism report last month that the letters have become increasingly threatening. Law enforcement officials have not released the letters to the news media, but Burton wrote that The Bishop began one letter mailed in June with the words "TIMES UP!" and threatened to mail up to three "packages" if a specific stock price did not "end green" on four specific days. A recently released sketch by postal authorities depicts him as being in his 30s or early 40s. Burton has pegged him between 25 and 35 but is unable to say so far what his occupation might be, or whether he has a family. Burton said The Bishop's belief that he can alter stock prices suggests he suffers delusions of grandeur. "He's progressing," Burton said. "He's taking his thoughts, which in his mind are reality. He's telling you what he's going to do and then he does it. He's heading down a garden path of violence." The pipe bombs, sent in white cardboard boxes, carried the same return address in Streamwood, Ill., and were postmarked Jan. 26 from Rolling Meadows, Ill. One arrived Jan. 31 at American Century Investments' Kansas City mail center, a few blocks from the company's headquarters. A day later, a similar explosive was found at a business in a 65-story skyscraper in Chicago. "It's almost impossible to be able to tell when he will mail his next devices," Burton said, "but he will."