A few things to note:
It came as a complete surprise to the 19-year-old daughter when the possibility to escape arose.
:: She recognised it was impossible to flee before. People would have not heard her scream in the cellar. Door only opened by security code.
:: Police appeal for people who have any information about the case to come forward.
:: Fritzl brought in food under cover of darkness for Kerstin, Stefan, now 18, and Felix who is five.
:: Those three, who were among six born in the cellar, never saw daylight:
:: The other three children were brought up by their grandmother, Fritzl's wife, when they were just one-year-old.
:: Fritzl also confessed to burning the body of one baby which died at birth. He disposed of it in the furnace of his building.
:: Josef Fritzl has lived at the property for 73 years.
Many more details are at the link.
The monster claims there was "no force" involved when he drugged, handcuffed, raped, and imprisoned his daughter for 24 years.

Looking at the basement photograph by Reuters, one wonders how he could have created this dungeon without anybody else noticing and questioning it. A lot of labor had to be involved to create this.