Drug traffickers armed with assault rifles opened fire on a bus on the outskirts of Rio de Janeiro, killing one woman and wounding seven other passengers, police said Friday.
An investigator said the motive for the shooting was not clear as none of the bus passengers had any obvious links to trafficking.
Drug gangs have in the past wiped out rivals inside crammed buses, injuring innocent passengers.
The bus came under attack Thursday night as it passed by the Rebu slum.
Police blamed the attack on a criminal group that controls drug trade in the slum and is battling over turf with a rival gang in a nearby slum.
The woman who died was traveling with her two small children.
The driver, who was unhurt, drove the bullet-ridden bus straight to a local hospital.
Many of teeming 600 plus shanty towns in Rio, Brazil's second-biggest city, are controlled by well-armed gangs.
Police do not patrol the poor areas and instead resort to military-style raids on the gangs, which often kill innocent people.
On Friday morning, in another part of crime-ridden Rio, residents of Vila Joaniza slum torched a bus to protest the killing of a young man by police in a raid.
A teenage girl and a small child were also wounded.
Police said they only shot back when greeted with fire by drug traffickers.