Two students accuse each other while their supervisor is also angry. Rather than immediately announcing punishment, the supervisor should regain composure, hear both sides, consider relevant evidence, and only then make a proportionate decision.
In وَهُوَ غَضْبَانُ, وَ links to the surrounding circumstance, هُوَ is a pronoun, and غَضْبَانُ describes the state of anger. The brief clause shows that the condition in which a decision is made is part of the ethical concern.