A couple and their four-year-old daughter were killed in a neighborhood in Rio late on Monday in suspected militia violence, Xinhua reported.
The incident occurred in the family's small cell-phone repair shop in the Anchieta neighborhood. Thiago Francisco, 34, was shot twice and his wife, Lidia Lopes Fontes 33, four times by a hooded man.
The couple's daughter, Taina, received a gunshot to head and was taken to the nearby Adao Pereira Nunes State Hospital but died in the early hours of Tuesday.
Local police chief Ricardo Viana de Castro, who is heading the investigation, said the shooting was premeditated.
According to witnesses, a man wearing a hood entered the store, shot the family and left in a silver GM Celta car driven by another hooded man. Nothing was taken from the shop.
The police believe that a local militia group, which controls the area, might be involved.
Militias, formed mainly by retired and serving policemen, and fire-fighters, are becoming increasingly common in Rio. They control poor communities and establish their own laws, charging for protection and monopolizing services such as transport and the distribution of gas cylinders.