This is an interesting philosophical question that really has little to do with what might potentially happen with an actual self-driving car. In the case of a real car, in the overwhelming majority of cases, it would simple stop and not hit anyone or anything. There’s no real way that 4 people would suddenly appear in front of a vehicle with sonar and multiple cameras suddenly enough that it wouldn’t see them well ahead of time with plenty of time to safely come to a stop.

A ball or even a dog might suddenly appear, or even a single person who stepped out in front of a car — but not 4 at once, and even in the case of the former, the car might well stop in time. I read about a Tesla automatically breaking for a balloon the blew across its path. In other words, this entire question is largely moot.