Why don't people cry when animals murder other animals?
It's not really murder.
Murder would generally be the act of willfully killing someone solely for the intention of causing their death.
Animals kill other animals either through accident (some larger animals, like dogs, can kill smaller animals, like cats, through play), or because of instinctual reasons, like hunting for food, or because their breed has been bred for hunting.
You shouldn't really be upset or punish a pet, like a cat or dog, if it kills a wild animal like a bird or rabbit, since it had no real control over why it was doing that.
But it is fair to be upset if they kill your pet, because obviously, it's your pet that you care for.
And in cases where wild animals kill domestic pets, like foxes killing cats or chickens, or wolves attacking sheep, then people will get upset and usually hope to kill or remove the animal.
Even in cases where a domestic pet, like a dog, kills a neighbours cat (or multiple cats) it may be put down as it's a dangerous animal.
