From what I understood from this song, it could mean one of two things.
The most popular opinion is that the song is about an alchoholic father/husband that regularly beats his wife (He's drunk again, it's time to fight). The child is thinking these thoughts in his head as all of this plays out in front of him.
There are a few lines in the song though that make me think that this isn't a child, but more along the lines of a neighbor in an apartment. Though "I hear her scream, from down the hall. Amazing she can even talk at all. She cries to me, Go back to bed. I'm terrified that she'll wind up
Dead in his hands" could be a child down the hall in a house, or in an apartment building, the lines "Been there before, but not like this. Seen it before, but not like this. Never before have I ever seen it this bad, she's just a woman" sound like an older person who has been around for awhile, and seen things like this happen before. (How many couples fighting do most kids see? Most see none, but some see their parents fight like this, maybe if they are very unlucky, after a divorce and remarriage, 2.) But from this line, it sounds like the "narrarater" has seen this happen numerous times throughout their life, but this is the worst.
After the husband beating the wife for yet another time, she eventually has enough and shoots him so he beats her....never again.