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(NBC NEWS) -- Kidnapping and rape suspect Ariel Castro is reportedly cooperating with investigators in Cleveland, sharing details of his alleged crimes against Amanda Berry, Gina DeJesus and Michelle Knight.

Ohio's attorney general ordered rush DNA testing to check for possible matches in other unsolved crimes. Test results have come back conclusive that Castro is the father of Amanda Berry's 6-year-old daughter, born while she was being held captive.

"This child kidnapper operated a torture chamber and private prison in the heart of our city. The horrific brutality and torture that the victims endured for a decade is beyond comprehension," said prosecutor Tim McGinty.

Law enforcement sources tell NBC affiliate WKYC that during an interrogation Castro was "cocky" and showed "no remorse," describing himself as "cold blooded" and unable "to control his impulses."