Soon after O'Banion's murder, Scalise and Anselmi secretly defected from the Gennas to Al Capone's Chicago Outfit. On June 13, 1925, Anselmi and Scalise, along with Mike Genna, ambushed North Siders George "Bugs" Moran and Vincent "The Schemer" Drucci in The Patch, shooting up their car with shotguns and wounding Drucci. About an hour later, as the shooters raced south on Western Avenue, they were sighted and pursued by a detective squad. After a high-speed chase, the gangsters were overtaken at the corner of Western and 60th Street. Immediately after the cars screeched to a stop, the gangsters jumped out and opened fire with their shotguns. During the ensuing gun battle, Chicago Police officers Harold Olsen and Charles Walsh were killed and Michael Conway severely wounded. The fourth officer, William Sweeney, pursued the fleeing Anselmi, Scalise, and Genna towards the next block of houses. Genna was fatally shot by Sweeney while the other two were captured after boarding a nearby streetcar. It was later said that when they were initially spotted by the detectives, Scalise and Anselmi were speeding south towards Chicago city limits in order to discreetly murder Mike Genna, who had allegedly been marked for death by the pair's secret employer, Al Capone.