Sounds to me like you were being proactive. Get 5 minutes with him, bring up the topic and ask him why? His reaction was probably symptomatic of another issue

Sounds to me like you were being proactive. Get 5 minutes with him, bring up the topic and ask him why? His reaction was probably symptomatic of another issue. By talking to him you can either figure out what you did wrong or hopefully get to the bottom of the issue that caused the reaction.