Anger is an outbursts of inner emotions. May be he is in trouble now a days in his career, or financially or any other factors.Give him support, empathy, and talk to him about his emotions and regular incidents. No direct question on anger.Just talk to him and give him full support .I think when his inner emotions are released and he will understand his problem then he will be ok. If help needed then consult psychologist or counsellor online or offline. Feel free to contact.

I think he is basically unhappy about himself.and problems seeking Attention and Appreciation. Also I think, it isn't a recent issue. Perhaps, he could have during his chi itself.