What happens if the last Shadow and Hunter die at the same time?
By a strict reading of the rules, the only requirement is that all of the opposing faction are dead, regardless of whether you or anyone else in your faction survived. Therefore, unless there is an official clarification to contradict it, all Hunters and Shadows win in this scenario.

Not much of a source, but this BGG thread agrees.

This would also mean that if a Hunter kills the last Shadow but also a third neutral at the same time, the Shadows would still win at the same time as the Hunters.