Am i crazy? My son is 5 and i need advice

Okay I would like to start off saying I know this isn’t a doctor’s office and I plan to talk to my son’s doctor about the situation but I guess I just want to know if I’m crazy or if other people have went through anything similar or maybe you just have any advice. It may be a bit long, so I apologize in advance…
So I have a 5 year old son and he is like most 5 year old children, loud, crazy, funny, smart and easy going but is also the sweetest boy, gives loads of affection and loves to be with people, especially his family and he loves to play with other kiddos, all except one (whom he has lived with not long ago for almost a year)… needless to say they fight like siblings almost anytime they are around eachother. Lots of pushing and hitting, taunting and such.
This weekend they were fighting on the play structure (and my son pushed him off, he says by accident and the other says he did it on purpose). When the incident happened and the little boy fell off the structure he began to cry and my son immediately started to cry as well and apologizing profusely, instant regret. I let him calm down a bit and then explained to him the severity of what he did and he was very sad, apologetic and wanted to know if his friend was okay. He then went with me over to the boy and told him he was very sorry and he didn’t mean to push him off the structure.
Fast forward to today, the other boys mom messaged me telling me my kid was psycho and he should be evaluated.
So I guess my question is (even though I’ll still be talking to his doctor) do you think my kid is normal/okay? This is the only instant where I have ever felt there may be an actual mental health issue with my child cause typically he would have never done this, he was very remorful and I have never thought there was anything wrong with him until this mom put these things in my head. Guess I just need some advice or just someone to listen to me cry, I struggle with anxiety daily and this is just too much for me to handle alone.