(sorry about the really bad drawing)
Two cars, A and B, are at an intersection. A is stopped at a stop sign; B is moving and does not have a stop sign. Across the intersection from B, there is a pedestrian in a crosswalk. The pedestrian cannot feasibly escape, and B does not appear to be stopping. B is far enough back that A could prevent them from hitting the pedestrian by pulling into the road. B is driving at a speed at which hitting a pedestrian would probably kill the pedestrian, but crashing into another car would probably not result in any fatalities. Is it legal for A to pull out in front of B, intentionally causing a relatively minor accident to avoid a fatal one? Is A at fault?