Relatives of victims of a 'massacre' protest holding posters that read 'Police violence in our communities', in front of a church in Nova Iguacu, Brazil, on April 2, 2005.  (AP Photo)

RIO DE JANEIRO, April 7 (Xinhua) -- Investigators of last week's massacre of 30 people on the outskirts of Rio de Janeiro announced a breakthrough in the case Thursday, with 12 policemen arrested and the car used in the shooting rampage found.

    Twelve members of the Military Police (PM) presumedly involved in the killings were arrested, among whom four were identified by witnesses and charged with murder. The car used by the murderers was found, officials said.

    The owner of the silver Volkswagen, allegedly used in the drive-by shootings, said he lent the car hours before the killings to Carlos Jorge de Carvalho, one of the suspects who had been chargedin the case, investigators said.

    Investigators of the PM, the Civil Police and the PM Intelligence Service had suspected that the massacre came as a reprisal by the renegade policemen for the moralization and disciplinary measures taken by the command of three PM battalions.

    Authorities believed rogue military police likely carried out the massacre in reprisal for the arrests one day earlier of eight officers suspected of another bloody murder.

    In an explicit warning to the commander of the 15th PM battalion, the officers killed two people, whose bodies were lefton a street, decapitating one of the corpses and tossing the head over a wall into the patio of the PM base.

    What the murderers did not know is that a camera located in theheadquarters recorded the scene, which allowed the identification and capture of the eight policemen in a matter of hours.

    The Regional Director of the Federal Police, Roberto Prel, saidthe main concern of the police is to gather as many clues as possible to have evidence against the indicted officers to preventthem from being acquitted for want of evidence, as has been the case in other cases. Enditem