American billionaire Thomas Lee committed suicide by shooting himself in the head at his Manhattan office on Thursday sending shock waves across the financial world, according to a report in the New York Post.

The philanthropist, who made his money as a pioneer of private equity investment and leveraged buyouts, was found in his office bathroom with a single gunshot wound to his head and his Smith & Wesson revolver next to him, the New York Post cited police sources as saying.

The 78-year-old Lee was discovered by a female assistant on the floor of the bathroom in his family office at the Fifth Avenue headquarters of his famous company shortly after 11 a.m. Thursday.

First-responders found Lee lying on his side with a self-inflicted gunshot wound to the head. Life-saving efforts at the scene were unsuccessful, and Lee was pronounced dead at 11:26 a.m., sources said.

The revolver found at his side was registered and licensed to Lee in New York City, sources said. The pistol’s license was in the office at the time.

The city Medical Examiner’s Office ruled Lee’s death a suicide Friday, listing the cause as a “gunshot wound of head.”

His modus operandi was to buy mid-sized firms and then grow them before selling them at huge profits.

Lee’s lucrative deals included purchasing Snapple in 1992 and then reselling it to Quaker Oats two years later at 32 times the price. New York state’s pension fund was Lee’s biggest fund investor for many years.