Some people are too eager to "shoot and hope". IMO, you should NEVER shoot if there's an alternative where nobody is hurt, even if there's loss of property.
Imagine if you saved your life and your family's life in a righteous shoot by felons who were planning to murder you. Do you care about the post-fall-out? You can't, you're alive.
Now imagine you ran out in the street and confronted some dangerous young thugs. You didn't HAVE to do that to save life. Now you're confronted with 'you shot my baby boy who only had a pellet gun and who saw you had a big gun - he tried to defend himself'.
It's a ridiculous risk he took and now he has to wait and hope the person's buddies don't come back and vandalize and torment him.
Basing your defense on hearsay like 'I thought he was racking the slide' is stunningly bad idea and sounds like an 'excuse' to get around the fact he ran up to them and had a gun out in the street. There's no Castle Doctrine in the US which justifies this.
Just my opinion. Most probably agree you don't go 'hunting' and expect to call it SD.