Venting
The fighting events had become a place where he could earn the attention of others and make up for what he was missing from his family.
He loved the praise and support he gained when he won a fight so it was easy for him to become reliant on it.
His loss against Ash was not just a humiliation for him.
It was almost like she had denied him what he believed he deserved.
What he wanted least was to have the crowd negatively view him and to remember his moment of loss and humiliation so it was better to remove the source that was tied to it.
It was not the first time he had done what he did to his past opponents that did not have anyone backing them,
If there was someone weak enough to become his target for hatred then he would use the opportunity he had to strike when they were vulnerable and did not suspect his involvement.