WATERLOO, Iowa -- A dog has fatally attacked a 9-month-old baby and seriously injured the child's grandmother at an Iowa home, authorities say.

Waterloo police Capt. Jason Feaker said that the 49-year-old grandmother was watching the baby at the child's home Thursday morning when the family pet, a neutered boxer/hound mix, attacked. He said the grandmother was hurt trying to intervene.

Patrol officers and other emergency responders went to the home, where the baby was declared dead. The grandmother was rushed to a local hospital and then flown to the larger University of Iowa Hospital, police said. Neither of their names have been released.

Feaker said the dog has been euthanized, and its remains sent to Iowa State University for further testing.