Turned syrup into liquor, can someone explain?

So I just recently made a batch of green apple syrup using sliced green apples and brown sugar, and it turned out great and syrupy. I then added some 86 proof Old Forester, 1/4th of a teaspoon, and a little yeast to maybe 1/3rd a cup of the stuff and put it in a flask for a week. I just opened it up and it’s a thin, kinda smooth whisky type solution. Can someone explain what it is? And is it safe to drink?