I had a creepy paranormal expierience?

So I live near Philadelphia and I went to Fort Mifflin one time. So there is this one building on the far end of the house. I went in earlier and looked around downstairs, not looking for ghosts just enjoying the sight. The stairs were boarded up so no one could get up. Later me and my dad were on the wall and we both saw this little kid, around 5 sitting in the window just gazing at us. We looked at him, and he looked at us, then he just vanished. I took a picture but it turned out bad. So I went back in to see how he got up there, but as I said the stirs were blocked so only someone important could get up. I called up and no answer. No one walked put and the only other way out is to jump out the window. So I got freaked out. Later me and my little brother got our phones and started recording things to see if we could get anything. We heard footsteps upstairs and we recorded them. I also thought I heard a moaning in the backround of the recording. It was just me and my brother, we were the only two kids in the building. No one else. So I never believed in ghosts. Later I heard a guy talking about how Ghsot Hunters was here. The volunteers started telling him about all the claims and told him there is a brochure about it. I got one too. So the story for that building was scary. Apparently there was a women who had three young kids, who all died in the room where I saw the kid. The description of one of the kids is exactly what I saw. Also you are supposed to hear the mom crying. Apparently this place is notorious for hauntings. I wasn't even looking. But this freaked me out. Was it ghosts, I am convinced. What do you think. And if anyone has ever been there let me know if anything happened to you. Thanks!