Hello! I am reviewing your piece as per your review request. First off let me say that this was a very interesting story but it was a bit too short to tell the whole story and to let your characters really develop. The character of Zep was a good one, however he seems rather dumb and naive, forgiving Aspen so quickly after she tried to kill him, believing James that he knew nothing about what caused Rosa to die, telling the gunmen to get out of his house before he calls the cops, of course he should call the cops, they tried to kill him.
Also, your story needs to go a little slower, the fact that everything happens within two or three days is rather fast and a little unbelievable. I, as a reader, knew instantly that James was behind the poisoning and that he was in on killing Zep. You want to try and surprise your reader. I will say, I was surprised that Aspen was in on it.
As for your grammar, I found nothing significantly wrong in the story. Please keep in mind these are my suggestions and I am in no way a professional. Thank you for choosing me to read and review this story.