Any human will be killed by an alien creature. On earth is included. They can be killed personally or via destruction of their ship. But it must be violent or physical. It can't be by for example, redirecting their food resupply ship so the human starves. It has to be violent or physical and initiated by the alien. Eg poison counts, electrocution counts, missile from alien ship counts, but persuasion to mistakenly destroy their own ship wouldn't count.

Creature can be intelligent or not.

Alien means of a species not from earth originally. Aliens born on Earth can count, if they didn't evolve on Earth.

Earth species born off earth do not count as perpetrators.

Mutated earth species born off earth can count, if their difference from earth creatures is significant enough at judges discretion.