This question can be interpreted in a few different ways, so I will answer it in a few different ways as well. The first interpretation is literal – who let the dogs out of the house or yard? In this case, the answer is probably a child or family member who forgot to close the door properly. It could also be a neighbor or passerby who saw the dogs running around and let them back into the safety of their home. The second interpretation is figurative – who is responsible for the current state of affairs? This could be interpreted in a number of ways, but some possible answers could be the government, the media, or society as a whole. The third interpretation is more abstract – what caused the current situation? This could be interpreted in a number of ways as well, but some possible answers could be a lack of understanding, a lack of communication, or a lack of empathy. Ultimately, the answer to this question depends on how it is interpreted.