How to help this student?

I have a student who showed me a note that was stuffed into their. It's extremely violent and uses homophobic slurs and it's someone threatening to harm him. I took the note and went to admin about it and admin isn't doing anything. They won't even look at the security footage to see who put this note in his locker and are writing it off as an empty threat. This child's parents also aren't helpful. He had already told me they don't accept him being gay and the second he turns 18 he has to leave so when I told the about the note and that maybe someone should pick him up from school instead of him walking they did not care and hung up on me. I'm not sure how else to help as it seems nothing will be done until something happens. I'm not sure who else to turn to for help😕