Who is the speaker?

My friend, David kept birds. He loves his birds very much. One day he phoned me, and told me that he was going away for a week. He asked me to feed the birds for him and said that he would leave the key to his front door in my mailbox. Unfortunately, I forgot all about the birds until the night before David was going to return. What was worse, it was already dark when I arrived at his house. I soon found the key David gave me could not unlock either the front door or the back door. I was getting hopeless. I kept thinking of what David would say when he came back. I was just going to give up when I noticed that one bedroom window was slightly open. I’m very happy. I found a stone and pushed it under the window. As the stone was very heavy, I made a lot of noise. But in the end, I man- aged to climb up and open the window. I actually had ’one leg inside the bedroom when I suddenly realized that someone was shining a flashlight up at me. I looked down and saw a policeman and an out lady, one of David’s neighbors. "What are you doing up there?" asked the policeman. Feeling like a complete fool, I replied, "I was just going to feed Mr. David’s birds. "But I don’t think they can believe me.