Police have arrested a suspect in the quadruple stabbing that left one bystander dead and three others wounded during an apparent robbery attempt outside an illegal gambling club in Sunset Park on Friday night.

William Smith, a 45-year-old Brooklyn resident, was charged on Sunday with murder, robbery, and three counts of assault. He is accused of fatally stabbing Yong Zheng, a 46-year-old who reportedly tried to stop the crime in progress.

Video obtained by the Daily News shows Zheng racing across the street to break up the brawl, then falling backwards and collapsing. A friend, Xiu Lin, told News that the recent spate of attacks on Asian Americans had disturbed Zheng, and that he believed he was intervening in a hate crime.

The victim had two children — a 14-year-old daughter and 4-year-old son — and drove a bus in Chinatown, his widow told WABC-7. He was celebrating the Lunar New Year with friends when he witnessed the attack. "He saw a crime, he tried to stop it," his widow said.

Members of the community are now raising funds for the family.

Two other men were also hospitalized with non-life threatening stab wounds, and a third person was treated on the scene.

The incident is not currently being investigated as a hate crime.

Smith is expected to be arraigned on Monday afternoon.