Nice. Gritty and well-written. I like the twist at the end.
You have some technical issues with grammar and punctuation. You need to go through and put in periods and such, and some of your sentences lack proper structure. Right now I'm a bit busy re-tooling the forum, but if nobody has helped you with that in a few days, poke me and I'll give better detail.
The description of the wings falls flat. "The shirt that was containing his torso" is awkward, and "the two lofty downy white appendages hung out from behind him" makes them sound sickly and freakish, but not in a 'wow, that's cool' way.
Otherwise the description is pretty good.
I like this sentence: "Jack wasn’t sure precisely what was bleeding, but he was certain it wasn’t a good sign." It calls to mind all those hard-boiled detective stories, and because the tone is so true to form, the sentence is evocative with an economy of words.
We have some links to sites that help writers learn proper grammar and punctuation, but they're a bit buried in the site. I am working on reorganizing so they will be easier to find. I recommend the OWL pages at Perdue University's website. Hope I got that name right.
Well, I am probably not the best one to help you out with punctuations, as I think it's what I have the most trouble with too (it comes from constantly mixing up French and English punctuations. XD)
I do think you could go "... that it would end like this: on the cold hard floor, in an ever increasing pool of his blood."
Speaking of which, is the expression "his own" actually considered bad form? It gets picked up by Word as by grammar and it is redundant, but I was wondering how bad it was and if it should be in the 'to avoid' list.
Nice beginning, Mick. A confrontation usually sets the mode well. As far as punctuation goes, re-read it and get the feel of how you would like the descriptions and text to go. If you have a long pause, or a continuation of a thought, you may want to use an em dash--it works well to indicate further description. The semicolon works well as a 'super comma', and allows you to link phrases that have more subordinant commas to be used; it's kinda like a list, but less formal; it sometimes adds a bit of drama.
Nice idea. The concept of the 'humanity' and 'inhumanity' of angels, and their like, has always intriqued me. Keep it up!