In [Schindler's list](https://en.wikipedia.org/wiki/Schindler%27s_List) there's a scene in which Amon Göth, the commandant of the concentration camp, [shoots some prisoners from his balcony](https://www.youtube.com/watch?v=FcyLRTB9fRY). His first victim is a woman that stopped to tie her shoes. [He shoots her, and behind her there's a small explosion](https://youtu.be/FcyLRTB9fRY?t=31). Why is that?

I've made a GIF of it:

[![Explosion behind the woman shot by Amon Göth](https://i.stack.imgur.com/60piN.gif)](https://i.stack.imgur.com/60piN.gif)

It can't just be the result of the bullet hitting the ground - unless he was using some special, explosive bullets. I know nothing about weapons and have no idea whether such bullets can exist, or could at the time of WW2, but [shortly afterwards he shoots another woman](https://youtu.be/FcyLRTB9fRY?t=55), and there's no explosion. And if the bullet was explosive, why is there no explosion when the first bullet hits the woman?

Is it simply an oversight on the director's part? I am not convinced, as it is quite visible, and it would hardly go unnoticed.

So what is that explosion? Why is it there?