Well not exactly. Some interpretations of thought experiments like this posit that simply being present for a situation and able to influence its outcome gives us an obligation to do so such that inaction itself is a morally unethical choice if we intrinsically recognize that zombies and people dying are bad and people living as not zombies is good.
We do know that zombies are creatures that try to kill people, and people are our group. Being something that tries to kill others is very clearly worse than not being something that tries to kill people. So we want as few zombies as possible, and as many people to survive as we can.