Carmela Dela Rosa told detectives she “did a terrible thing” when she flung her 2-year-old granddaughter to her death off a six-story walkway at Tysons Corner Center, according to a taped interrogation played in court Tuesday.

Dela Rosa, 50, is charged with murder in the November 2010 killing of Angelyn Ogdoc. Her attorneys are presenting an insanity defense at her trial, which began Monday in Fairfax County Circuit Court.