While Boston-based accountant Harry Markopolos was a notable outspoken skeptic of Bernard Madoff's supposed investing prowess, it turns out there were others who had questions about the Ponzi schemer's proposition. But, the Post reports, they did nothing. Documents filed with the SEC reveal that three senior executives from Citigroup, Goldman Sachs and Write Capital had their suspicions but never contacted their superiors or the SEC. The Post writes, "The silence by the executives is disturbing to some, who claim a second alarm bell could have forced the SEC's hand and brought Madoff's alleged scam to an end sooner." However, "A source close to Citi said [former employee Leon] Gross should not be singled out, as his views about Madoff were commonplace on Wall Street, adding that Gross did not spend much time analyzing Madoff's investment strategies." The director of the SEC's enforcement division, Linda Thomsen, announced her resignation last week.