why is jean valjean so mean to petit gervais? how do his actions connect to the themes of the novel?

Jean Valjean is a desperate man. He has just got out of prison (19 years) for stealing bread. He is starving and humiliated. I don't think he is angry at the boy rather than his situation. This boy has money and he doesn't. Jean steals a 40-sous coin from 12-year-old Petit Gervais and chases the boy away. He feeld badly after this.