Transcript for 'Humans of New York': Photog Gone Viral

A photographic melting pot, joy, pain, wisdom, beauty, pure cuteness and they are brought to you by this human of new york, a lovable guy named brandon stanton. Excuse me, I was wondering if there's anyway I can take a photo of you just like this? I'm an artist. Reporter: He approached over 10,000 strangers this way. And what they give him gets shared on facebook millions of times a day. He has a limited knowledge of camera settings and photo shop software his first book is about to land adopt the best seller list and although he never posts pictures of himself. I'm a huge fan. Reporter: Somehow people know this is the guy that moved them. A guy that connects them one honest portrait at a time. Thank you. Have a great day. Reporter: It's like being with the mayor, are you kidding me? Pretty incredible considering three and a half years ago he was a stressed out bond trader in chicago. Two events changed his life. First he got a real camera and then he got fired. I lost my job and I woke up. Now have all of this thought energy to put into any direction I want. Reporter: What he wanted was to take pictures of interesting strangers. My mom basically thought this was my glorified way of not working. I'm serious. Just like, oh, brandon is in new york taking pictures of people on the street and putting them on facebook, you know what i mean? We're so proud of him. Exactly. So here I am doing this all day long with absolutely nothing to show for it. So this went on for six months i photographed every single day. I photographed on christmas eve and christmas, new years eve, new years day, all day long. Reporter: He built a modest following but then he started actually talking to his subjects and much to his surprise he learned people are more willing to open up to a stranger with a camera than to even their best friends. She said when my husband was dying, I said how am I supposed to live without you? And he said take the love you have for me and spread it around. And her voice was kind of quivering and the rain is coming down and I said thank you very much. I turned the corner and just started crying. Reporter: He started posting these along with the photos and the following exploded. If I follow you on my facebook feed, there's a completely different feel I get from what you put up as opposed to even some of my best friends. Yeah, because everything on social media and facebook is so stage managed. You get everybody's highlight reels. Social media is secondary when I'm having the conversations on the street. You get the full spectrum. You get the tragedy. The uncut humanity. Exactly. Reporter: Overtime he learned it's not what you say to a stranger but how you say it. It's all about the energy you give off. For me, that's about making yourself as nonthreatening, genuine, natural as possible. I like this guy. I'm going to ask him. I was wondering if there was anyway I could take your photograph just like that. Reporter: Two out of every three say yes and he knows just how popular that yes will be. Over 30,000 likes. Over 30,000 likes. I can tell after a minute where it's going to be after a day. All right. Here we go. 14 seconds, 60 likes. 24 seconds, 164. That's incredible. Reporter: And this community gives more than likes. Case and point, the time he met a little boy selling a blanket full of cowboy supplies so he could buy a horse. I pulled his mom aside and said if we could get a horse, is this something you would want. And she started crying and said we live in a small new york apartment. What he needs is a dog. Reporter: So he asked his followers to kick in a few bucks to send him to a dude ranch and in less than an hour had $30,000 in donations. You look great. Reporter: It's easy to mock the old cultures that believe a camera can steal the soul but humans of new york is a kind of photography that makes you wonder if they're right. And if it makes you feel differently about that passing stranger if your big city or small town. No smile. You told me a sad story. Reporter: Well, that makes brandon stanton one happy guy. I'm bill weir for "nightline," new york city.

This transcript has been automatically generated and may not be 100% accurate.