Image via WikipediaI find the Fireworks explanation mildly weak for the bird kill. There were multiple simultaneous bird kills that were not all caused by a small fireworks display. Also, the simultaneous fish kill is not explained by fireworks since fireworks don't work very well under water. It could easily be coincidence or it could be the government not wanting to alarm anyone to avoid a panic over an imminent earthquake. Hey, I have watched the movie Dante's Peak so I qualify as an expert.
Fireworks likely cause of massive Ark. bird kill - USATODAY.com