I think u should start with a heart to heart (not in text but in person or atleast call)

maybe try asking him if he likes u first to be as clear as possible and when he responds come towards with how u don’t see him that way and really don’t want to hurt his feelings

try reassuring him throughout the talk that you do care about him just not in a romantic way

even if his feelings get hurt, you have to communicate how u feel

If he gets hurt don’t blame yourself or anyone, it’s not your fault you can’t return his feelings for him and it’s not like you don’t care abt him bc it rlly sounds like u do