Riot police in the Brazilian city of Sao Paulo have clashed with other police officers who are on strike.
The confrontation happened when the striking officers tried to force their way past barriers to reach a building used by state governor Jose Serra.
This is what happens when the police attack each other.
Follow this link, enable Java scripts- its only 1 min 29 second long.
http://news.bbc.co.uk/2/hi/in_depth/7675316.stm