The incident happened around 1:24 p.m. at the Check 'n Go on the 12000 block of Central Avenue.
Investigators say two men shot the female clerk, robbed the business, and then took off in a four-door Nissan Altima.
The first suspect was described as a Hispanic male about 20 years old with a medium build. He was wearing a Boston Red Sox baseball cap, a light gray hooded, zip-up sweatshirt, black pants and black shoes.
The second suspect was described by police as a man with a dark complexion, possibly Hispanic or African American, about 30 years old with a stocky build. He was wearing a dark-colored baseball cap, dark hooded zip-up sweatshirt and dark-colored pants.
A $10,000 reward is being offered for the arrest and conviction of the suspects. Anyone with information was asked to call the Chino Police Department at (909) 628-1234.