What's behind mysterious booms?

SignOnSanDiego.com > News > North County -- What's behind mysterious booms?: "Life can serve up a good mystery every once in a while. Weird things happen that defy explanation, that make us wonder how much we really know about the world. Something of the sort happened in San Diego County shortly before 9 a.m. Tuesday, April 4, and so far no one has come forward with an explanation. "