On July 5, 1978, Harris and his younger brother commandeered a car occupied by two 16-year-old boys, John Mayeski and Michael Baker, ordered them to drive to a remote area, then killed them. The brothers then used the boys' car as their getaway car when they robbed a San Diego bank. Harris was arrested less than an hour after the robbery and charged with murder, auto theft, kidnapping, burglary, and bank robbery. Coincidentally, one of the arresting officers, Steve Baker, was the father of one of the murdered boys, but did not realize that fact until later. Robert Harris was convicted and sentenced to death on March 6, 1979. After a series of appeals and stays of execution, Harris was executed in San Quentin's gas chamber on April 21, 1992.
Harris' execution is specifically remembered for his peculiar choice of final words (recorded by Warden Daniel Vasquez): "You can be a king or a street sweeper, but everybody dances with the grim reaper," a slight misquotation of a line from the 1991 film Bill & Ted's Bogus Journey. His last meal: A 21-piece bucket of original recipe KFC chicken, two large Domino's pizzas, a bag of jelly beans, a six-pack of Pepsi, and a pack of Camel cigarettes.