This makes sense because Hannah’s mom is seen at a shooting range using a gun, and she also admits that she wants Bryce dead. She must’ve been very angry at Bryce in order to say that, considering the fact that her lawyer was right next to her when she said that. Her anger is also expressed through the fact that she said “god-f*cking-dammit,” again right next to her lawyer, in reference to her anger caused by Bryce’s lack of punishment.
P.S. Montgomery is seen as violent whenever he’s upset. A great plot twist would be for Monty to kill his former best friend. Former best friend, because, keep in mind, Bryce betrayed Monty in the last episode of Season 2, which was still after Montgomery had lost all other friends. In addition, in his Season 3 picture, Monty’s newspaper mentions him antagonizing Bryce, which must’ve been caused by a very, very strong change in character. Plus, we all know what antagonizing led to with people like Tyler. Bryce has an abusive dad, no friends, and, seemingly by nature, a violent personality... why not him to kill Bryce, the one who left Montgomery stranded and switched to another school?