Perhaps he is depressed,or maybe he has issues at home and thats why he is attention seeking,or he could be having some odd teenage phase,there was a boy a bit like this in my year at school.He used to talk about death loads,and vampires,and once he brought a knife into school and then he got kicked out for a bit.Teachers said he was depressed.I think the best thing to do is just keep quiet about it for now and if anything else happens that worrys you I`m sure the members on here will tell you wether or not they think you should tell someone one.The worst thing you could do though would be to talk about it at school becuase if it is attention seeking your just giving him what he wants and he will probably just keep craving it and doing/saying odder things.