> What change was the person who shot him hoping to elicit?

This would be a relevant question in many nations, but it's a bit beside the point in the US. Violence is a deeply respected and loved core of the culture for its own sake. It's an end, not means. Nearly all the US's entertainment, culture and myths are built around a reverence for violence. Even political violence has been pretty much the norm through most of the US's history. Celebrated cases aside, there's been something of a lull since the mid 1970s, but if as now likely it increases again, this will be a boring old reversion to the US's norm.