Facebook Inc. fired a senior manager for buying shares of the social networking powerhouse in a private, secondary-market transaction last September — four months before Goldman Sachs Group Inc.  announced its investment in Facebook, the Web site TechCrunch reported Friday, citing multiple sources.

The share purchase by Michael Brown, who worked in corporate development, allegedly violated Facebook’s rules on insider trading.

The New York Times’ Bits blog later Friday cited Brown as saying, through an emailed statement from his lawyer Edward Swanson: “I did buy Facebook stock on the secondary market in early September 2010, and I did so with the absolute best of intentions and only because I believe in Facebook.”

Apparently referring to the TechCrunch report, Brown said: “False and damaging information has been published about my actions.” He added that he had no knowledge of the Goldman Sachs deal “until it appeared in the press in January 2011.”

Facebook fired Brown a few weeks ago, the Times reported, citing people with knowledge of his dismissal.