Transcript for Mayor at Center of 'Poopgate' Resigns
Neighbors from hell continues. Reporter: Neighbors. You can't choose them. Judging by a quick trawl of youtube, there are a whole lot of neighbors from hell out there. Even in the most genteel surroundings like here in sleepy, sunny San Marino, California, neighborly relations can explode. In this country, when someone puts On your doorstep, they're telling you what they think of you. Reporter: That's what happened. And it's dirtied the name of San Marino. When they think of San Marino, they're gonna think of the poop zone. Reporter: Watch the security camera evidence. A man picks up a bag of dog poop, not from his own dog, it was just lying on the sidewalk, and flings that feces onto a neighbor's doorstep. I was stunned. This is shocking to the whole community. Reporter: Because the man caught on camera lobbing that little numero duo, none other than the man in the big chair, the mayor. And mayor Dennis kneier has gone the way of Nixon, he resigned. We've been trying to get in contact with you about the whole dog poop thing. Well, I haven't gotten any messages. And I'm really busy now. Reporter: He's just woken up. Are you a psychologist? I'm not. And neither am I. And I can't answer your question other than to say it was a mistake. I was tired in the time that I did it. It was a mistake. Reporter: Dr. Ari Novick is a psychologist -- an anger management expert. We all have made judgment errors. He said he was tired. Deprivation can do that. But there's never an excuse for throwing feces on your neighbor's yard. Reporter: The neighbor in question is this guy. He says, "It got a little bit heavy, and I decided to drop it." And this little bag was less than half, you know, a pound. Reporter: Was a small dog. It was a small -- yeah, a small dog. Reporter: Philip Lao is a regular thorn in the ex-mayor's side. Now making political capital out of projectile poop to stop mayor kneier's agenda in its tracks. He's proposing painting bike lanes along the road. We had fought against the tennis lights. Reporter: So you are a concerned citizen, not a pain in the butt? That, well, that -- that's what I would think, you know. Reporter: Lao thinks this was an act of vengeance. Did you have a beef with Mr. Lao or -- No. Nothing. No. Well, we have disagreements in terms of he comes to the city council and he objects to things. Reporter: Has it ever crossed your mind to throw poop at his house? Yes. You know, when I saw the video and I thought, hey -- hey, since he can do this, I can do. But my wife talked me out of it. Reporter: If you live in a city, chances are you have a neighbor from hell nearby. Comedian Hal sparks has one. I have a neighbor who has a tree. A gooey, sappy tree with white fluff. It tars and feathers my house. Your neighborhood is a family you didn't choose. Reporter: But these days security cameras, like Mr. Lao's, make it much harder for those nasty neighbors to get away with it. Steve miller lives in posh palm beach gardens, Florida. One day he noticed a bag of dog poop on a bush in his manicured front yard. Then I noticed there were another ten bags in there, so I went to the store. Bought a video camera. Mounted it on the house. Just let it run. And it caught all the action. Reporter: A dog-walking neighbor was regularly dropping doggie doo-doo off at Steve's house. On this video evidence, he was given multiple tickets and a little punishment to fit the crime. They also made him come back and pick up his droppings. Reporter: All 11 bags of -- video is now a deterrent. Or should be. Imagine if there was a hidden camera viewing everything you did, how would you wanna be seen by others? Reporter: Some now take the law into their own hands. Publicly shaming them with a play by play critique of their late night karaoke playlist, posted in the building. If you're going to be woken up after two hours' sleep, it might as well be to a herd of morons singing "Tiny dancer." He ended the review with three simple words, "I hate you." That's the way to handle it. It's charming. It uses creativity. It embarrasses them. It gets the entire neighborhood on your side. Reporter: And you haven't behaved badly! The missing journalist
This transcript has been automatically generated and may not be 100% accurate.