What angered the police was the attitude of firefighters who turned up to help deal with the car accident in which Mr Mason and his son Grant, 20, were involved.

In the video, the police struggle to make the arrest as two firefighters watch with their hands in their pockets and another holds a flashlight. None help the police try to control the situation.

At one point, a firefighter appears to try to step in, but a colleague urges him back as the struggle continues. Finally, a senior police officer rushes in and delivers three quick whacks with his baton. He then uses the baton to gesture at the firefighters watching, and when police handcuff Mr Mason and his son, the officer points a threatening finger at the firefighters. Words are exchanged.

'Our members have certain expectations [from other emergency workers] when we're at emergency calls,' police spokesman Constable Howard Chow said. 'Those expectations were not met.'

The altercation angered many in the Vancouver police force who consider the inaction of firefighters an unbrotherly act.

Unfortunately, when the police trying to arrest Mr Mason realised they needed help and backup was called in, two patrol cars collided, sending four officers to hospital. They crashed, coincidentally, near a fire station and were immediately helped by firefighters.

The injuries, none of which were life-threatening, enflamed an already explosive situation and Vancouver's police chief, Jamie Graham, sent out an internal memo, later made public, to calm things down. 'We have a close and positive working relationship with the Vancouver Fire and Rescue Service and them with us,' he said. 'I would ask everyone to keep this in mind as we examine more closely the circumstances of this event.'

For his part, Mr Mason said the attack was completely unprovoked. After the incident, he had seven stitches under a black eye, and sore ribs and back.

Mr Mason said he and his son were out celebrating St Patrick's Day and he was a passenger in a car that collided with another at a downtown intersection. When police arrived and asked for identification, Mr Mason said he motioned towards a female family friend who was the driver and the next thing he knew, police tackled both himself and his son.

The 13-year service veteran said he had gone through all the possibilities in trying to understand why police were so rough with him. 'I'm still trying to find a reason to believe, to give them the benefit of the doubt in my mind,' he said.

He held his hands up at a press conference to show that he had no marks, scrapes or bruising and could not have been trying to fight police. 'It doesn't matter how I look at it - they overreacted.'

Now it is his turn to react. He has filed a complaint with the Office of the Police Complaints Commission and hired a lawyer to consider suing the police force. When he was thrown in jail, Mr Mason said police directed their anger at him over the injuries to the four officers involved in the later accident.

Bob Smith, the fire department's acting chief, said it was important to get a full picture of what happened that night. 'By and large staff of both fire and police realise that this is nothing but a hiccup in our relationship,' he said.

No matter who threw the punches, both departments have ended up with a black eye.