I have one big problem, the speech should be on a new line, then it feels less like you have to read it in one breathe.
Also a little help to make it more interesting
Posted by: agent waffle
the marine pointed up towards a building, just then a thin beam of light flashed tearing two of his fingers clean off, splattering his hand with dark red.
To make that better i would do this:
the marine pointed towards the top floor of a building, suddenly a thin beam of light pulsed, two of his fingers were torn off, leaving bloody stumps and crimson red blood splatters over his arm and torso.
just a few minor alterations and additions. However when dealing with a sentence like that, try not to make it carry on for too long as it tends to bore the reader.
Other than that it was great.
Don't just edit that part of the text, use mine as an example and then reread your story and see what could be improved and improve it!
:D