I have personally done some target shooting. I live in the middle of a redneck BFE portion of Ohio, and I hear people shooting off guns a lot. I can tell you that in my neck of the woods, gunfire rarely consists of one shot, so its identity and location aren't too difficult to verify. If, however, there was a loud, sharp noise that only occurred once in an area where gunfire could potentially be a bigger problem than a bunch of drunken idiots during deer season, I can see how confusion might occur.
Also, the comments above about the unreliability of eyewitness accounts are entirely correct. No matter how intelligent or well-meaning a person may be, our memories are more faulty and easily influenced than most people realize.