Jonathon Quarles Jr., who lives in Indianapolis, was spending the day Sunday with a woman described as his step-grandmother. Police said he died after the attack in the woman's home.
The death is being investigated and an autopsy was to be performed Monday.
According to Montgomery County Animal Resource Center records, an American Staffordshire terrier is registered at the step-grandmother's address. The breed is a middle-sized dog that resembles a pit bull.