PITTSBURGH (AP) -- The Pittsburgh Zoo & PPG Aquarium says the mother of a 2-year-old boy fatally mauled in a wild African dogs exhibit is to blame in her son's death and shouldn't be allowed to sue. The claim filed Monday in Allegheny County is in response to a lawsuit brought by the parents of Maddox Derkosh. Jason and Elizabeth Derkosh are seeking unspecified damages in the Nov. 4 death of Maddox, who fell over a 4-foot-tall railing into the exhibit after his mother lifted him up to get a better look. The zoo says in the court filing that Maddox's death was "caused solely by the carelessness, negligence and/or recklessness of Elizabeth Derkosh." The parents' attorney, Robert Mongeluzzi, said in a statement Wednesday that "the zoo's position is dead wrong and shameful."