<human>: Can you condense the text into a few key points?

The short version of events is he was looking after his girlfriends son. He let her son play with a piece of a broken beer bottle and the poor kid cut his hand open. The broken beer bottle was my brothers and the cut was deep and he needed to go to the hospital. 

I am actually good friends with my brothers girlfriend. She was the first friend I made when I moved to America with my family. She broke down crying today and was distraught that she was not there when her son was bleeding and how scared he must have been.  

My brother told my mom exactly what happened and she told me. She told me to not say anything because my brother will never speak to us again. I want to tell her because he lied to her about what happened when he cut himself.
<bot>: Brother let hid girlfriend son play with broken glass. The kid cut himself and he lied to his girlfriend about how it happened