Hi M.,
I'm in agreement with the other posts. He's developing his ability to have insight into himself and his choices and that is completely age appropriate. Along with development of insight comes development of empathy, another very important factor in moving through the world.
I would say make sure you keep the communication as open as possible. Reassure him that he can talk to you about ANYTHING without judgement or recrimination. Reassure him that everyone needs to review events in their days and examine them. Tell him that by doing that by talking with you about them, what my parents would call "debriefing" is a very valuable thing. And that you are a safe place for him to do it. If you feel an opening then make a suggestion. Another tack is to ask open questions like "have you thought about it this (fill in the this blank) way?
Obviously, if you see this having a major impact in his functioning, such as him not attending parties or events, or withdrawing from his friends and school and such, you might need to intervene a little more intensely. Too much of anything can become a bad thing. Look for signs of depression and/or anxiety and call in a professional if you feel it's warranted.
These years are at least, if not more challenging, than the toddler years. They are growing just as quickly body, mind and soul. Try to love him through this phase and use these experiences with him to empirically prove he is worthy of love and support. And when he goes through this with his kids, he'll have your example to look back on for guidance.
thoughts to you and yours, S.