A "rocky" experience

There is a first time for everything I suppose. And as a mom of three boys - it had to happen sooner or later...
We got a knock on the door this afternoon from one of our back-door neighbors. She came to tell us Carson was throwing rocks over the fence and almost hit one of the kids in her backyard. In her fist she held a rock the size of a tennis ball.
Seizing the opportunity to teach Carson a life lesson, I promptly took him around the block to ring the doorbell and apologize to all parties involved.
"Carson, this is a good opportunity to turn a bad choice into a good choice. What should we say when we get to Mary's house?"
After some prompting and discussion, he practiced the line, "I am sorry for throwing rocks over the fence. I won't do it again."
We reached the house and Carson rang the doorbell. Simultaneously, the invisible rubber band that was very short, and very strong snapped Carson back to my side and wrapped him around my right leg.
Of course the mom knew exactly why we were there (she was SO kind about the whole ordeal and was SO understanding), and led us into the backyard where she was entertaining her guests which included a small pool full of kids.
Carson froze. Shocker, right? There were tears, threats, hugs, and a whole lot of fear.
The sweet kids stood there wide eyed in the pool waiting so patiently for Carson to "make it right". They kept encouraging with phrases like, "It's okay". "Don't be sad, Carson." "Thanks for coming to say sorry."
In the end a muffled and shakey "sorry. I won't do it again" came out of his mouth. Lesson learned.
While it wasn't my favorite mommy moment, I was grateful for Carson doing something that was hard for him, and "making it right".
Any guesses on how long it will take for something like this to happen again?