It happened around 5 p.m. in the 6800 block of Beechnut Street.
Police said the baby's father had left him in a bouncy seat to go outside and turn on a sprinkler system. He returned to find the dog attacking.
The baby's mother walked in and also tried to help. She was bitten twice.
The baby was rushed to the hospital, but did not survive. The Dallas County medical examiner's office identified him as Brayden Wilson.
The father shot and killed the dog shortly after the attack, police said.
Police are still investigating the case and a grand jury will likely determine if charges will be filed against the parents.
CPS said it is also investigating and that there's no history of problems involving the family.
Family members declined to discuss what happened with FOX4.
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