Who killed Robin’s parents?

The Tragic Fate of the Graysons

The youngest member of the renowned acrobatic family known as the Flying Graysons, Grayson witnesses the horrifying murder of his parents by the mafia leader Tony Zucco, who sought to extort money from their circus employer. Following this tragic event, Bruce Wayne takes Grayson under his wing as his legal ward and later mentors him to become his crime-fighting partner, Robin.