I heard a dog barking in a closed down school, what should I do?

Ok so I was playing basketball today at a closed down school and I went close to the doors which were barricaded and I heard a dog barking very loudly and whining, I wasn't the only one hearing this people playing basketball as well were hearing the dog too. I went to check around if it wasn't just coming from outside but I was pretty sure it was coming from inside. At this point im really clueless and have no idea what to do, any suggestions?

I probably would of just went in looking for it. But if you think there is a dog in a dangerous area, or a dog hiding in there because it doesn't have a home or something, you should tell someone that can help it. (If your too afraid to try yourself)