I'm wondering if this really constitutes a threat. "I wish you would die" is not the same as "I am going to kill you". One is a passive statement of a desired state and the other is indicative of pursuing action. Try this on for size: "I wish I could fly" and "I'm going to jump off this building because I can fly".
I recognize that I perspective is not popular in this day and age but this just sounds like some kid being a wanker, not someone meaning to kill.

