I once read that citizens who carry legally, are less likely to use a firearm illegally than LEO are.
IIRC, I read the same thing, and that they 4 to 5 times likely to hit the bad guy. I believe it was in numbers stated in the DOJ's annual Uniform Crime Reports or the National Crime Victims Survey. I believe John Lott may have written about it. As far as LEOs being more trigger happy, it makes sense because as gov't employees they are indemnified, unless they do something outrageously stupid violating gov't guidelines which exposes them to civil liability.
Well not quite. It concerned lawful gun owners, whether carrying or not. They are less likely to shoot the wrong person than the police. Actually it's quite understandable. The armed civilian is there when the crime occurs, and knows who the bad guys are. A policeman coming upon a crime in progress, or where one has just occurred, doesn't know who are good guys and who are the bad guys. Good guys sometimes get shot that way.