The man who calls himself "The Bishop" and who has sent six threatening letters and two dud pipe bombs over the past 18 months is expected to strike again, the Associated Press reports. One of the pipe bombs was sent to American Century on Jan. 31. Then, on Feb. 1, a similar explosive was found in a Chicago office building.

But next time, given that "The Bishop's" letters have become increasingly menacing, the bombs could be real, warns Stratefor counterterrorism expert Fred Burton.

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