No, you can't kill a dog - and sarah I'm sure if the dog actually harmed someone they'd report it...
...let's not get too excited about this ok? overthinking leads to problems of your own manufacture - avoid it....
...And I actually love dogs. More than cats. But not more than cute babies
Scimi
EDIT:
think for a second - has anyone attempted to feed it? it is a stray... as Muslims we are ViceRegents on this planet - caretakers over the animal and plant kingdom - why are we not fulfilling our obligations to the animals? Dogs are not evil.
Consider this, a dog cannot talk - it barks - it is hungry, it barks at a human because it is used to receiving its daily provision from a human. It wonders why no one is feeding it, it is crying out to Allah to send someone who will feed it - it is tamed through its master and lost its instinctual nature to survive and hunt - thus it stays in the locality it is used to - the familiar surroundings. Dogs are immensely loyal animals, the most loyal animal in the world - more loyal than any friend you will make most likely - and Muslims usually give dogs a bad rap simply because their saliva is impure?
What kind of heard hearts have we fostered in our selves? It makes me sad to read posts such as the OP.
I had a dog in India, well, my father took in a stray in 2011 and when he came back to the UK - do you know who took the responsibility for it? An Aalim in my village - TRUTH I swear it - when I was in India in 2012 December - I saw the dog with my own eyes in the care of this aalim who is pious and loving, a real gem of a man who makes Muslims of the modern age look brutish in their treatment of dogs.
I tell you something, the west gets a bad rap sometimes for all the wrong reasons, such as being dog lovers - but I tell you now, that the non Muslims of the west who have dogs, are more attuned to the fitra of "viceregent" than we can ever be.
All this talk of killing an innocent, hungry and lonely dog has really made me sad.
Give it some food, go buy it a tin of dog food and see what happens. The dog will folllow you, love you and guard you. They are loyal creatures - and one more thing, they see Jinn, and so, can act as a forewarning because they bark at the empty spaces - this lets you know it is barking at an unseen entity - a warning for you to make dua of protection before something bad happens.
Please do not kill this dog - do not enter that sin.