Lemme make this as simple as I possibly can... "Never let the muzzle cover anything you're not willing to destroy."
If you back your car outta your driveway without verifying that there is no one behind you... and you kill someone... that's simply not excuseable.
Similarly, if you pull a trigger, without verifying your target AND backstop... and that round kills an innocent bystander... that's manslaughter.
*