I see you have your location as NY. if this is new york state usa a bit of info here in ny it is very common for 4th, 5th on up through high school to say things like I want to kill myself, someone just kill me already, dont you just want to die and other suicidal/ death phrases. if its not accompanied by any other symptoms then its nothing to worry about, just a slang/ fad/ children expressing their frustration over their homework or friendship problems even their dislike when parents say something the child doesnt like.

periodically here in the USA children and teens change how they talk. watch any documentary from the 70's and you will find lots of words to the effect of dying, getting stoned (drugs) the 80s movies and documentaries are full of the valley girl phrases, the 90's was full of "dont you know" and "bite me" phrases.... the 2000's were full of harry potter phrases and here we are in the next decade where the in thing is suicidal, self injury phrases like I want to kill my self, just die already, someone kill me now and there is even tattoos that represent these phrases that children and teens are getting.

my suggestion is sit down with the child and find out why your child is saying it. kind of like if someone says oh with a swear word a parent would turn around and say why did you say that and where did you hear that one. if the child is actually suicidal have the school psychologist check in with them or take them to a child and family therapist who can work with them.