American public school perspective, here, but death threats were a normal part of the bullying equation growing up. Sure, it was mostly "we're going to kick your ass after school", but there was the occasional "we're going to put you in the hospital or the morgue" and just enough follow-through to make the threats credible.
Calling this bullying isn't inaccurate, the severity of bullying has been downplayed. It isn't just stealing your lunch money and calling you ugly.
Bullying is exactly the correct term for this. You just don't appreciate how evil bullies actually are.