Five years prior to Joker War, Bao's parents were killed by the Joker. Batman was able to stop the Joker from causing further damage, leaving one of his batarangs as a result. Bao kept the batarang as a memento. A couple weeks after Joker's henchmen began wreaking havoc on Gotham City, Bao saw a handful attacking a nearby store. Realizing that Batman won't arrive to stop them, Bao attached the batarang to a wooden bat and set out to take matters into his own hands.