In May 2008, former Lehman Senior Vice President Matthew Lee wrote a letter to senior management warning that the New York securities firm may have been masking the true risks on its balance sheet. A month later, he had been ousted.

His warning was revealed for the first time in a report by a U.S. bankruptcy-court examiner and showed that Lehman's auditors knew of potential accounting irregularities and allegedly failed to raise the issue with Lehman's board. Here is the letter that placed the little-known Lehman executive...