That's the difference between a hardcore felony like manslaughter and a misdemeanor like a DWI or smoking weed. The manslaughter charge is a mistake that will follow you for the rest of your life. Even if you get away with it. The latter will not.<<Emphasis added.>> So you get into a fight with another dude, pull out your gun, blow his brains out, run away, live a clean life for the next X years, and you're not a criminal? Really?
OP probably got arrested for shoplifting or something really dumb but not really a big deal. Shooting someone in the head is not in the same category.