Why Did French Bank's 'Rogue Trader' Do It?

"He apparently leaves very early in the morning and comes home very late at night," said Jacqueline Cuny, another neighbor who said she had lived in the building for 40 years and that Kerviel had been there for "about three or four," although she had never met him during that time.

It was unclear how recently Kerviel had lived there. The note on the mail boxes said his apartment had been sublet. Genevieve Morand, 91, another neighbor in the building, said she saw him once in the last 10 days and he was carrying two briefcases.

Anne Gillier, who works in a nearby real estate agency, said she had regularly seen Kerviel in the neighborhood -- although not for the past one or two months -- and that he stood out.

"He was physically seductive, always elegantly dressed. But he was always alone," she said. "I never saw him with a woman, or even with another man, I always saw him alone."

No one answered what was believed to be Kerviel's mobile telephone number. "Hello, you have reached Jerome's mobile, I'm not available at the moment," said an even and steady man's voice in the recorded message.

Employed by Societe General since 2000, Kerviel worked his way up from a supporting role in an office that monitors trades to a job on the futures desk where he invested the bank's money by hedging on European equity market indices. That means he made bets on how the markets would perform at a future date.

Going beyond his role, Kerviel took "massive fraudulent directional positions" in various futures contracts, the bank said, betting at the start of this year that markets would rise. The bank says his actions cost it 4.9 billion euros ($7.18 billion). It has not explained his motivations and said the transactions didn't earn him any money. Executives said he seemed to be irrational.

"When we interviewed him during the night Saturday and Sunday, he imagined that he had discovered methods able to win money on the markets," said Jean-Pierre Mustier, chief executive of the bank's corporate and investment banking arm, on Thursday.

Using his knowledge of Societe Generale's control systems, gleaned in his former monitoring role, he escaped detection. Most of his positions went unnoticed by colleagues and superiors as Kerviel covered his tracks with what the bank described as a "scheme of elaborate fictitious transactions."

He got caught when markets dropped, exposing him in contracts where he had bet on a rise.

Kerviel, described as a "brilliant" student by one of his former university teachers, both shocked and impressed executives with the complexity and scale of his trades. The bank's CEO called the fraud "extraordinarily sophisticated."