The story broke because Elizabeth (The daughter who was held Hostage so many years) needed to get medical attention for Kerstin (One of the Children of the incestious relationship). Josef agreed to allow Elizabeth to attend Kerstin at the Hospital (Her first time out of the cellar) and she contacted the Police.
The full story is located at
http://www.belfasttelegraph.co.uk/news/world-news/fritzl-confessions-from-the-cellar-13877171.html
Theologian
4 Yrs Navy payroll, 1 Yr Civilian Pay, 7 Yrs preaching/Bible Teaching, Attending Boyce Bible College