Josef Fritzl: a shrewd liar and an obsessive tyrant

Police say Fritzl also threatened his daughter and the three children held captive with her that the cellar was rigged to release toxic gas in case they attempted to overpower him in a bid to escape.

Herbert Katzengrueber, Amstetten's mayor, said City Hall officials who dealt with Fritzl described a manipulative and controlling man.

"He was apparently very dominant within the family," Katzengrueber said. "He terrorized the family. The deplorable acts against the daughter were not the only violence. There was also permanent pressure put on the family over the years."

Fritzl was born in Amstetten on April 9, 1935, but little is known of his early life. Even his parents' names have been withheld by authorities, who say privacy laws prevent them from releasing birth, marriage and death certificates.

A class photo from a school trip in 1951 obtained by AP shows a 16-year-old Fritzl looking tall and handsome, with dark hair and a serious demeanor. A former classmate who gave his name only as Erich S. recalled Fritzl as a "slightly different" teenager and remembers his unfashionable haircut.

Johann Kreitler, director of the high school Fritzl attended from 1947-51, said Fritzl left school at 16 and later went to a vocational school.

Fritzl's employers and colleagues say he gained their respect and was a hard worker.

"He expected a lot from others, but he seemed to expect a lot from himself," said Graf. "Saturdays, Sundays, holidays if work needed to be done, he did it."

Yet outside the workplace, there were warning signs.

Reports suggest Fritzl was arrested in the 1960s in Linz and may have served prison time. Police have declined to comment, saying records that old have been erased under Austrian law.