More callers... Everybody painting a different story. Odds are good that many of the callers are hoaxes, IMHO.
Keep posting. Remember the (Tom Clancy?) novel that had the plot about an attack on a mall? Personally, I doubt that they'd pick Tacoma on a Sunday afternoon, but you never know.
I would suspect it's probably thugs shooting thugs and being pursued by plainclothes police or security.