(NEWSER) – Navy Yard shooter Aaron Alexis carved two cryptic messages onto his shotgun before Monday's shooting spree, investigators tell the Washington Post. One said, "Better off this way," and the other said, "My ELF weapon." The Post observes that ELF generally refers to “extremely low frequency" and notes that Alexis had told police only a month ago that people were harassing himwith a "microwave machine." Related? It's anyone's guess at this point.