Along with a colleague, the 54-year-old volunteer policeman spotted that a man in his thirties had punched someone in the face in front of a bar, police report.
But as the volunteer cops tried to intervene to cool things down, the situation only escalated. First the man struck one on his head so hard that he later had to be treated for concussion.
He then attacked the second volunteer officer, brutally biting his ear off.
The wild attack did not slow down when the professional police arrived. The man repeatedly tried to hit one policeman over the head, and to steal his pistol from its holster.
Police say that the volunteer officer's ear could not be sewn back on in hospital.
The aggressor was found to be carrying a kitchen knife in his inside pocket. He already had a history of violence and has been held in custody.