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We've said it before and we'll say it again: Mess with Jamie Dimon and you do so at your own risk. Last fall, during the bleakest moments of the financial crisis, the JPMorgan CEO began receiving threatening letters from a man who was angry about losing money a chunk of money following JPMorgan's acquisition of Washington Mutual. The anonymous letter-writer didn't just threaten to kill Dimon and promise to "McVeigh" the bank's New York office building. He also included a bit of white powder in one of the envelopes, which set off an anthrax scare at JPMorgan HQ. Duff McDonald recounts the episode in his new book on Dimon, Last Man Standing: The Ascent of Jamie Dimon and JPMorgan Chase:

Dimon later received a letter containing white powder and a note that read, "Steal tens of thousands of people's money and not expect reprercussions [sic]. It’s payback time. What you just breathed in will kill you within 10 days. Thank xxx and the FDIC for your demise." More than 50 copies of the letter had been sent to multiple Chase bank branches, the FDIC, and the OTS. Dimon's letter also contained a reference to the "McVeighing of your corporate headquarters within six months." All were postmarked Amarillo, Texas.

The FBI didn't have much luck tracking down the person who sent the letters. So, naturally, Dimon took matters into his own hands. He turned to the bank's security team, which apparently includes a bunch of former Secret Service agents and CIA operatives, and they located the man. The bank then turned over the information to federal authorities and the suspect—a man named Richard Leon Goyette who also went by the alias Michael Jurek—was arrested. Four months later he was convicted and sentenced to 46 months in prison.

One moral of the story: While you might consider sending an unsolicited package in the mail to Citigroup CEO Vikram Pandit or Goldman Sachs chief Lloyd Blankfein, it's probably a good idea to steer clear of Dimon.

Jamie Dimon's Anthrax Scare [NYT/Dealbook]