If two adults set out to pursue a child that didn't do anything wrong but was in the company of other children one of of whom may have done something, and the child flees and in being pursued trips and falls and injures himself, are the adults criminally or civilly liable? For this question, I have in mind the situation that can be seen in this video clip: https://www.youtube.com/watch?v=5f5G6sUVaXE
If the pursuit is unlawful (which it almost always is except for police) and the pursued suffers harm in fleeing from the pursuer, then the pursuer is responsible both criminally and civilly.
Being pursued would put a person in fear of harm: that’s the criteria for assault so the act of pursuing someone without lawful cause is a crime. Self-defence ceases to be a defence when the other person is running away - even if they are carrying your TV. You can use reasonable force to effect an arrest but a pursuit is not likely to be reasonable if it is of any significant distance or involves vehicles. Police pursuits are strictly limited and police have been successfully sued when they exceed those limits and harm comes to the pursued.
If the pursed dies, pursuers can and have been convicted of murder or manslaughter.