FWIW, I was threatened on Reddit more than once with actual murder... people threatening to come to my house and kill me. Reddit's general response was to... delete the chat message in question as a "resolution" to my complaint. AFAIK, that was the extent of their action. I at least have the impression that abusive users will be removed, though it might take a bit given the incredible influx of new users.
This is horrible, why do people think they can say this shit? I hope you reported this to the police? I'm pretty much most places this behaviour is illegal. It's not a good look for Reddit to be complacent with illegal activity on their site.
DrChickenbeer