With this new info I would 100% make the school aware this is happening. First of all they may be able to do something based on it being in text, but also I would just want the admins and teachers to know about this interaction.
In case you didn’t know, since you’re in TX be aware that the school can now intervene in student harassment/bullying/etc even if happens outside of school under David’s Law.
I’ve pieced together the highlights of what happened. I hope that child and their parents understand what would have happened had this happened at school.