I Won't Be So Careless Again!

One day I went out and left my key in the house. When I came back, I found I couldn't get in without my key.

What should I do? After a moment, I got an idea. I picked up a big stone and was ready to break the window. Suddenly there came a deep voice, "What are you doing?" I turned over and saw a policeman was behind me. It took me quite a long time to explain myself. I won't be so careless again.