If you are just getting into writting poetry, I suggest studying the different types of structure to get a basic knowledge. Now, personally I despise "formated structure" for writting but the reason why I think you (and other people) should start writing with structure is so that once you've learned the "rules" you can break them to make it better. I guess think of it like a famous painter. They know all the rules for using color, composition of a piece, but then they take a certain aspect and break the rule. I think this can only be done properly after you've learned about structure and other rules.
I think the poem is a nice start, though a bit rough. You have some rythm and flow in certain areas, but then it gets hard to read in others. This can be used as an tool to help convey the story, but I do not think you did that on purpose. Again, the reason I stated the above paragraph.
I applaud the fact that you did not try to make every other line rhyme. It is refreshing to see that. Be careful in how you word things because you don't want to sound archaic (an expansion on talloulou's "I must haste" comment... actually, it would be "hasten" I believe. So, if you do want to word it like that, double check your sentence structure and how you are using the words to make sure it is correct.)
I like that you added details like the girl dressed in grey. Maybe make "as the bullet sounded" more concrete. How did it sound exactly? Too often good poetry will not be great poetry from the use of vague terms and expressions. You really want to place the reader in the situation of the character, but you can't do that when you use vague words.
Now, to really confuse you, I liked how you did not give a clear detail to the "foe." It allows different readers to relate to the foe. Hehe, so vagueness can be used for good.
I hope I didn't confuse you too much. Like talloulou said, take it with a grain of salt. Even the famous poets have people who hate their work. You can't satisfy everyone, and you should only write for yourself.
, if you do re-work the poem, I'd love to see it.