I have a 10yr old daughter and the boy in her cl wrote her a note saying he was going to kill her what do i?

well it happened yesterday on h the bus on the way home and i have had trouble with this little boy ever since my little girl was in 1st grade what can i do about it ive called the law on the little boy and called the school and dhs and i dont know what else to do about it because in the past the school said that they would take care of it but they dont