Set aside for the moment the possibility of the former and the gross irresponsibility of internet "news" sources in reporting otherwise if that were the case, and consider the latter possibility . . .
. . . is this an act worthy of condemnation?
Towards an art exhibit in a country where thousands of dogs die on the street on a yearly basis, in an age when human life is carelessly tossed after unnecessary wars, from inhabitants of a country which cannot honor its own treaties, which imprisons 100,000s for victimless crimes, which itself has violated the most hallowed international rules of conduct, come condemnations of the death of a single street dog.
 Judge not, that ye be not judged.  For with what judgment ye judge, ye shall be judged: and with what measure ye mete, it shall be measured to you again.  And why beholdest thou the mote that is in thy brother's eye, but considerest not the beam that is in thine own eye?  Or how wilt thou say to thy brother, Let me pull out the mote out of thine eye; and, behold, a beam is in thine own eye?  Thou hypocrite, first cast out the beam out of thine own eye; and then shalt thou see clearly to cast out the mote out of thy brother's eye.  Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest they trample them under their feet, and turn again and rend you.
Matthew 7: 1 - 6.
The death of animals is not at the same level of contempt as the death of humans. To hollow the lives of animals irrationally diminishes the value of human life. If the act of killing an animal has the same status as killing a human, then surely the other acts we (acceptably) perform towards animals should also have the same (acceptable) status for humans. These include, of course, holding captive, forcibly removing the sexual organs, performing (fatal) scientific experiments upon, slaughtering for food, raising in cramped and unpleasant quarters for the purposes of slaughtering for food, keeping chained in cages for our viewing amusement. The important point here is that animals and humans are de facto not morally equal because they are not treated equally. To appeal in one moral area for equality is to appeal also for that equality in another area.
But surely, even if allowing a dog to starve for art does not have the same moral status as allowing a human to starve, we can condemn it? On what grounds? That suffering of dogs simpliciter is wrong? Surely, then, our efforts would be better spent helping those dogs living on the streets of central and south america? (But perhaps this was the artist's point? - but surely then working towards saving living dogs would be far more constructive than condemning him for making this very point?) Surely our efforts would be better spent liberating the 50,000,000 captive neutered dogs in the US before protesting the change in quality of life of a single free dog which died after only a day of captivity? Or is the life of the "happy" slave the one we endorse for dogs? Again, this only helps the standard to seem more palatable for humans.
Note: the point here is not that killing a dog or allowing it to die is a "good" thing, but rather that the effort and emotion expended upon protesting this one event indicate a profound lack of respect for the dignity of human life on the part of the protestors. The undesireable actions [murder, torture, suppression, enslavement, etc.] perpetrated upon human beings in a systematic fashion in this age are simply too numerous to justify any energy whatsoever geared towards defending the "rights" or "well being" of animals. Such an action is not only profoundly hypocritical, but undermines the defense of human rights which should be our first priority.