Investigators in Brazil are investigating whether police officers killed at least 12 young men in a number of incidents across the city of Campinas to avenge the murder of a colleague.
The wave of killings began on Sunday night and continued into Monday in Campinas, about 60 miles north west of Sao Paulo.
The mostly drive-by shootings of the young men occurred within about four hours of one another and came after an off-duty police officer was killed while fighting armed robbers who targeted him as he stopped at a petrol station in the same region. Police investigator Licurgo Nunes Costa said:
We're not ruling out executions, revenge nor a fight between criminals. It's a sequence of events in the same region and around the same time and we have to consider the relationship between the occurrences.