In my country brushtail possums are a rapacious introduced pest (along with weasels, stoats, hedgehogs and even rats), and conservation involves continuous efforts to kill them and then stop them from reinvading from neighbouring properties.
I much prefer killing them in a trap so I don't need to do the dirty work by hand, but someone somehow does need to kill them. I admire the author for confronting this reality, and I'm sure next time she'll do it in a far more effective way that is less stress for everyone.
People in a modern urban environment (in the US, anyway) don't understand how to grow a vegetable, raise a chicken, filet a fish, mill flour and bake bread. Less than 100 years ago, everyone knew this, because almost everyone did this. But modern urban creatures are like the possum's babies - constantly feeding from the teet of a system that insulates them from real world concerns.
My mom (who lives on the 300 acre family farm) was complaining to my first cousin (who holds several state bow hunting records and at one time had a hunting show on cable TV) about how hard it was to keep the raccoons out of her vegetable garden. "How did the pioneers manage to grow vegetables?" she pondered out loud.
"They would have eaten a lot more raccoon than you do" was his reply. And he was absolutely correct. Coon, possum, squirrel, and groundhog were all on the menu in my neck of the woods well after World War II.
I agree with this. But note that people disagreeing with the author's actions are not necessarily against the killing of animals that threaten your livestock: this is a necessary reality. The issue is that this author does so in an apparently irresponsible, inhumane way. It is not necessary to torture animals.
People that use the term murderer already know that the state wouldn't get a conviction.
Also, "murderer" is a really harsh term to throw around for someone who kills pests, even if they really suck at it and have no idea what they're doing.