Overreacting? Threats on the bus.

Yesterday my son (6) got off the bus and was visibly upset. He told me that there was a kid "B" that he hated on his bus. This set off little bells because we don't use the word hate in regards to anyone. So I asked him what happened and he told me that B has been telling him that he's going to kill him, every day- for sometime now. How long, I'm not too sure as a 6 yr old is a bad judge of timeframes. With some gentle questioning I gathered that this kid is in third grade and always sits next to my son. What prompted my kid to tell me yesterday was that apparently B told him that he's going to get a knife next christmas and he's going to "cut off your head and hang it on the wall in my house."I tried to ask only the basics, has he ever put hands on you, what's his name, what exactly did he say and to just be calm and say that I was going to take care of it. I didn't want to make it out to be a big thing even though inside I feel like it's a big thing. My son also let me know (and I was vaguely aware) that K and 1st graders can only sit in the first 3 rows on the bus and once you pick a seat you can't move but this B kid can sit further back and he always sits next to my son. He told me he thinks he annoyed B (he knows he talks WAY too damn much) and that he has tried to stick up for himself lately by telling him he doesn't like him and yesterday telling him he hated him.I plan to go to the school monday morning but my one encounter with the principal has been less than great. She was cold, the opposite of empathetic and brushed me off. I am super anxious that this will happen again. I don't know if I'm making this bigger than it needs to be or not enough or what because it's my kid. What do you guys think? via /r/Parenting http://ift.tt/2jAM6oV