Which always struck me as surprising. Batman: The Animated Series was unable to show the murder of the Waynes due to FOX Kids's strict censorship on violence, so all they could do was allude to it through the occasional dream, hallucination, or news clipping. So I would've expected that the greater freedom they had in Mask of the Phantasm would've allowed them to dramatize it at last, but they didn't take the opportunity. (Then again, the film's co-writer/producer Alan Burnett had already penned the first animated adaptation of Batman's origin story eight years earlier in the Super Powers Team: Galactic Guardians episode "The Fear," which remains one of the only times the scene has ever been portrayed in animation.)
Batman:The Brave and The Bold had a episode that showed, in nearly perfect execution, the deaths of Thomas and Martha Wayne, down to the scattering pearls and everything.