Not bad. You've definitely mastered the use of your own voice, which already makes you better than a lot of other writers around!

I see what you tried to do with presenting your little exposition, but I think it came out very sloppy. You threw together basic information about the situation to set the scene when it could be handled with a little more precision. You kind of jump around what's actually happening because you're leading up to it, but that really takes away from what the exposition is supposed to do. You also made sure to include some character traits at the start so that readers could begin getting emotionally invested (well done - nobody likes being kept away from the protagonist), but I'd love to see a little bit more of that.

You were obviously very caught up in the intensity of the scene; you write like I do, in that I think our power shines through our dialogue. But there is so much of it without any pause for description or anything that it speeds up the flow and can make a reader feel a little lost.

But I did not mistake the lack of description for weakness. It brings the story as a whole down, but there's a lot of valuable power in the words of your characters (who are very interesting - please tell us more about them before leaping right into action, otherwise you'll lose us)! It's great that you started doing that at the end, but you ought to spread that sort of description and characterization around the entire chapter, rather than keeping it in a few paragraphs at the very end.

Overall: less dialogue, more description and characterization. Remember the number one rule of writing: show, don't tell.

Otherwise, I liked it! Good start!