Does mediation of criminal minor injuries require all parties to be present?

Not all of them, but there is a premise that the suspect and the victim reach an agreement and fully implement it.

But the key point is that under the condition that the investigation is not over, the arrested suspect cannot contact with others, including the victim, except the lawyer; China's criminal mediation system is a traditional way to solve civil disputes through effective methods under the auspices of the people's courts according to the provisions of relevant laws and regulations, and to urge the parties to private prosecution criminal cases or criminal incidental civil actions to reach an agreement on litigation issues. Therefore, when the case is transferred to the court for trial, the court can preside over mediation. If an agreement is reached and compensation is made, the sentence can be reduced for several years as a discretionary mitigating circumstance. (Moreover, if the victim gets full compensation, he can claim compensation from the other two fugitives after they are arrested. )

The other two suspects who are at large can pursue the case online and handle it separately.