After reading this, the only answer to the question "who" is "federal forces". I don't believe in drug addicts being able to shoot like snipers.

http://quake.wr.usgs.gov/prepare/future/

I always thought that people buying dry food and water because they were afraid of terrorists were... taking a little too many precautions. Now, after looking at New Orleans, I am thinking of the same to prepare for a possible Bay area earthquake. You can't evacuate for a quake.