In that regard, the Great Ghost Dance can be looked at under two different perspectives. It was a massive act of sacrifice magic, that put the Scourge closer. But its goal was also to trigger multiple volcano eruptions (possibly including, though the original SR writers had no way to know at the time, the Yellowstone supervolcano). Had the Great Ghost Dance went ahead, a volcanic winter could have drastically reduced global population.
So the Great Ghost Dance could be considered as purposefully designed to either fasten up or slow down the coming of Horrors. One might even wonder if firing the Lone Eagle ICBM at Russia wasn't an early attempt at lowering Earth population by some millions.
So the Native Americans were the ones planning mass murder? That has to be a popular conspiracy theory. :|
The Native Americans
performed the Great Ghost Dance, but I never said they were the ones who
designed it. Spirits, half-horrors, dragons or whatever taught the shamans the dance may have had very different goals indeed.
But even if they weren't planning to kill hundreds of millions of people, the SAIM was at war and certainly was not playing nice. Triggering the eruption of Mount Hood, Mount Rainier, Mount St. Helens and Mount Adams was their last warning shot. Let's just remind that Mount Rainier is about twice as big at Saint Helens and in direct proximity to Tacoma. There were none of the usual, sismological warnings. It was also said Chief Thunder Tyee ordered his units to help evacuate some area near Mount Rainier (after the eruption), which suggest the state and Federal agencies were not capable to do it. Several hundreds of people killed may be a conservative estimate. That may not be a lot with regard the global deathtoll on both sides between 2009 to 2018, and it was only a fraction of the number who would have been killed if the US government carried out its extermination campaign. So I think it depends if you consider "mass murder" only as a synonym for systemic genocide or if you consider that isolated acts of wiping out entire villages qualify.
There would be an interesting moral debate considering whether the Ghost Dance shamans had fine control or not over which volcano would erupt, and then if the eruption of Mount Rainier (likely to be the most deadly) was necessary to display the power of the Ghost Dance.
Besides, the eruptions were only supposed to a warning shot. So the plan had to have a next phase. If you consider that volcanoes cannot erupt twice, there weren't so many options available to raise the bar. The eruption of the Yellowstone supervolcano would jump directly to the hundreds of millions killed (albeit indirectly over several years). Earthquakes in New York City (again), San Francisco, Los Angeles and Seattle may kill "only" a few thousands of people, while causing disproportionate economic damages. Massive floods along the Mississsipi, Colorado and Los Angeles rivers may leave more time for evacuation, while still causing massive economic damagas (and, interestingly enough, devastate the areas that would delimitate the NAN, possibly allowing the SAIM to expand its control zones).
Of course, that would assume the casualties among the Ghost Dance shamans did not prevent a second strike. What the Great Ghost Dance was capable of after the eruptions would indeed be one of the best-kept secret of the NAN even several decades after, for strategic reasons.
Back in 2009, taking over a military base and launching a nuclear missile at a random target, on the other hand, certainly qualify a "planning mass murder". But as far as conspiracy theories go, I still wonder what the Shadowrun authors original idea was. We all take that event for granted because we read about it in various sourcebooks set forty years later. If former members of the armed forces were to take over a military compound in the most remote part of Montana for ten days, before the Delta Force kills them all, what independent sources of information would you actually have ? Sure, the media would rush to whatever is the closest Montana town, but I doubt they would be allowed to settle anywhere near the base. So the best independant evidence you would have would actually be some shooting of a missile fired up in the sky. The book specifically stated no explanation was ever given on how the terrorists entered the base, and doesn't given one regarding how they bypassed the missile launching protocols
Actually, there is no military facility anywhere near Shiloh Valley in Montana... (though I guess it may a fictious place modelled after Malmstrom Air Force Base, near Great Falls)..