I think the reoccurring lawnmower sound effect was a good touch. The story was also very well told and edited. Good job!
I think this is a great story but it feels like the end needs a little work. There is this build that happens in the exchange between the narrator and his dad that sort of creates suspense for a climax. But then nothing really happens and it's just "oh that's my neighbor." I think you could fix this by editing down that exchange between father and son and have it take up less time in the piece. I do really like the description of them running to the window together and I think the lawnmower sound is effective. Although I would think about where you are placing it in the piece because it kind of competes with the narration in some spots initially (it could just be a levels thing though). I also really appreciate his vivid description of the neighbor and how after you first hear the lawnmower it fades a bit and then meanders through the stereo field. This is nice because it really puts the listener in the scene.