original_query: What evidence linked Ong to the double murder?
query: What evidence linked Ong Hwee Kuan to the double murder of Lee Kim Lai and Chew Theng Hin?
answer: Ong Hwee Kuan was linked to the murders because a police officer saw him behaving suspiciously near where the taxi was abandoned; Lee's body, with 15 stab wounds, was found in the taxi; and Chew's body was found in a drain the next day.