"Bright early, a baby is shot and killed and it was avoidable," said Stewart.
The death happened around 9:45 a.m. in the 2400 block of Sturtevant, near La Salle Blvd.
Stewart said a 9-11 call came from the house shortly after the gun went off. When they responded, police provided medical attention to the child who later died from their injuries.
Detroit police have recovered the firearm, identified it as a Glock.
"This is why we emphasize gun safety with gun locks and lockboxes," said Stewart.
Another 1-year-old was in the house, as well as a grandmother.