Violent video: Police used ax to beat people

This is a video from Dingzhou, Hebei, China.

Police version of events: Police rescued a girl from an organized MLM (multilevel marketing) group, but the girl refused to leave the police station. Family members came to the police station and attacked police.

Hard to believe: If family members came and saw the girl, why would they attack police?

Even if they argued with police, do police have the right to kill people after they fell to the ground?