Police `` will not rest '' until they find those behind killings in Campinas , official says . Authorities are looking into all possibilities , including whether it was a police revenge attack . Comment: However , fans from around the world are expected to flock to nearby Sao Paulo , the country 's financial and business hub . Angry residents took to the streets and set buses on fire to protest the killings .
Police `` will not rest '' until they find those behind killings in Campinas , official says . Authorities are looking into all possibilities , including whether it was a police revenge attack . Comment: Angry residents took to the streets and set buses on fire to protest the killings .