Riverside police said the puppy, a "Bichon-poo," was in the back yard of a home Saturday afternoon when the home owner heard her older, 70-pound, dog howling, the Chicago Tribune reported.
The owner found the puppy with severe wounds to the abdomen. The smaller dog died Tuesday.
The owner said she did not see a coyote but a veterinarian said the wounds were consistent with a coyote attack.
Police recommended owners accompany pets outside and keep them on short leashes.
Riverside is located along the Des Plaines River, and there is a lot of wildlife in the area, officials noted.