While we generally define murder as 'unjustifiable homicide' ranging in degrees from one to three ('premeditated' to 'reflex crime of passion'?), the objective ethics of cases like this suggests that the unnecessary, unjustified killing of a sentient mammal should become criminalized and prosecuted as 'fourth degree murder'.
LOL! Who do you think you are, coyote?
Agreed!
At some point we humans will have to come to terms with exactly what levels of sentience, sapience, intelligence, self-awareness, and consciousness constitute a being which should be respected and treated as we would expect to be treated -- as sentient, sapient, intelligent, self-aware, and conscious beings. One day we may realize that this applies to dolphins, whales, chimps, and perhaps even horses, canines, elephants and other mammals. One day this may also apply to artificial intelligence -- given that it has a level of sentience, sapience, intelligence, self-awareness, and consciousness which constitute a being which should be respected and treated as we would expect to be treated -- as "people" (even though they are not "human").
One day we may encounter other beings from other star systems who may regard humans as NOT being adequately, in their perspective, sentient, sapient, intelligent, self-aware, and conscious to be regarded as no more than slaves or perhaps no more than animals to be hunted for sport.