I saw a kid leave his bike outside the store today and remembered how I had left mine outside the library when I was in 6th grade. I used to ride my bike to the library and look at all the plane, train, and military books. One day, as I was checking out my books, a kid got on my bike and road off!!!
I was having none of that, and I chased his butt! The kid was pedaling as fast as he could but I was catching up and he kept turning around looking at me with that "OH $HIT I'M GONNA DIE!!!" look. Evidently he was riding to his house because I was just about to catch him and his dad stopped him, and gave me my bike. He smacked him and yelled at him for a bit, and I wondered if it was for my benefit so I wouldn't kill him.
Even though I didn't return that day to get my books, they were set aside for me by the librarian. The next day, I bought the toughest looking chain and master lock for my bike, and used it when I checked out the books! ;)