Killing for "fun"

I really don’t understand the mentality of the people who could do this-

http://www.bbc.co.uk/news/uk-england-devon-11624253

I can understand having to kill for food, to protect family or property, but why on earth kill such a magnificent creature as a mere “trophy”? What is so clever about taking a gun and killing a dumb, defenceless animal? And before anyone calls it “sport” name me any other sport so ludicrously one-sided.