I have a 14 yr old girl and they are going through a very emotional time finding out who they are. Middle school is tough....you are friends with 1 group 1 day and outcast another....the ups and downs are NOT fun. I personally don't see your son having a "hard" heart, I see him figuring out who he is.
Now, rest assured...you will get plenty of responses claiming he has some mental disorder and needs therapy and meds. Who knows, that might be true but I am a firm believer that parents are over drugging and over counseling kids instead of being there and talking to them.
Fortunately, we are ok behavior wise but we have seen mood changes on occasion and heartbreak over friendships. Some of the girls are cruel. I happen to have a popular girl with a lot of friends in several groups. One thing she does have.....friends from different groups such as her orchestra friends are different from all the cheerleader friends which are different from the preppy and skater friends. She is also active OUTSIDE the school for friends as well.
She is aware that yelling at me or my husband is crossing the line and when that happens, we take her most prized possession, her iphone. It does not take many times for that to happen and she si right back on track.
It does get better!!!!!!!!! We are very open minded and have lines of communication with nothing off limits. She knows we will always listen to her, even though we might not agree with her. Be there for him ready to pick him up emotionally and help maintain his self esteem.
I know it is hard, hang in there.... We've been married 20 yrs and the ages of 10-13 were the worst (SO FAR)
TF