Brazil police investigated over three-hour killing spree in Campinas
14 January 2014 Last updated at 02:10 GMT
An investigation is under way in Brazil to find out whether a group of policemen went on a three-hour killing spree in an alleged revenge attack.
Twelve people were killed overnight by gunmen in vehicles in a district of Campinas, a city north of Sao Paulo.
The BBC's America's editor Leonado Rocha reports.