Four gun-wielding men opened fire and killed 27 persons Thursday night in the metropolitan region of Rio de Janeiro, said police sources on Friday.

According to the Public Security Secretariat, the four gunmen first opened fire on a group of people near a bar in the district of Nueva Iguazunear, killing 15, including three teenagers.

The four gunmen then moved on and fired on pedestrians in the center of Rio de Janeiro, killing 12 more persons.

Brazilian police are investigating the incident.