A few things to consider:
1. Is this a matter of confused neighbors, a conspiracy against the main character or a mix of the two? While the sound of a gun being fired from far away and a gun being fired extremely close are very different, if it's a matter of confused neighbors, what sort of trouble could their muddled, panicked thinking cause the main character? (Another thing to keep in mind is that eyewitness accounts of crimes are often
terribly inaccurate. Ditto with suspect line-ups; you'd be amazed how many innocent people get ******** over by the judicial system due to inaccurate or flat out false eyewitness accounts. Might be worth doing some research on those subjects)
2. If it is indeed a conspiracy against the main character, how far does the conspiracy go? One thing to consider is that, as the position of District Attorney is often an elected position as opposed to an appointed one, many a district attorney has not been above hiding or destroying evidence that proves the defendant guilty just to improve their conviction rates on paper. Not saying all DAs are scum...just saying some really don't like to lose. You can read up on a prime example of such
here and
here. And those are just two higher-profile cases of wrongful imprisonment due to overzealous and/or corrupt DAs. There's no telling how many more people have been imprisoned or even put to death despite their innocence because some a*****e withheld evidence.
3. Not every town's police force has a forensics team--while common in larger cities, smaller towns don't usually have a CSI team and have to call one in from another town for crimes that absolutely require collecting a lot of forensic evidence. So if your story is set in a larger city, yes, what Sir Icehawk stated would be 100% correct as far as what the forensic team would pick up from the scene and checking your main character for GSR. If in a small town (and doubly so if there's a conspiracy afoot and the police are involved within it), however...more often than not, the detective in charge of the scene likely isn't going to bother with forensic evidence (or even so much as bother to note that the angle of the fatal gunshot wound is completely inconsistent with a frontal close-range shot) and will just use the statements collected from neighbors as probable cause to detain your main character.
If you decide to have the main character surrender to the police and need some info on how to make their time sitting in county waiting for their indictment, pre-trial and all that jazz sound realistic, I have quite a bit of information about the subject handy that I'd be more than happy to share with you. Now, I will make the disclaimer that some of my knowledge may be Texas-specific (while *knocks on wood* I have never been arrested or charged with a crime, in the the past few years I've had far more dealings with the Texas legal system than I
ever again want to have for the rest of my days due to my ex-fiance), but from the research I've done for my own book, no matter what state you're in, county jail and prison really doesn't change much because of location.