So how does it feel to live in the most heavily armed society in human history? Do you take fear or comfort from the fact that this country holds three times more gun stores than McDONALD'S... See More
So how does it feel to live in the most heavily armed society in human history? Do you take fear or comfort from the fact that this country holds three times more gun stores than McDONALD'S RESTAURANTS? For many, it took a slaughter of en and children to start talking about the 34 americans shot to death every day, and that talk has many others lining up to buy their first gun. So at this moment of national conversation in a search to understand the complexities driving both sides, "nightline" teams fanned out across one nation under the gun and deeply divided. Philadelphia, 7:30 p.M. Sergeant john hoyt works overnight. A shift that makes a reasonable man question how anyone could ll this the city of brotherly love. And just moments into his night, it begins. Right now, a man was just shot in the face. Actually, it's just a boy. 17-year-old. Shot during a robbery. Riding along and bearing witness to this all too common ritual is our pierre thomas. Reporter: This is a city that has 3,000 shootings per year. And more than 300 homicides so far in 2012. 85% involving guns. This is the story playing out in big cities across the nation. Night after night. Shot twice in the face, once in the back. They can't give us a definite. It's very serious. He's extremely critical and he's in the trauma bay and they're doing everything they can for him. Sergeant hoyt knows his night is just beginn and it would be the night of the sound of gunfire popping over and over and over again. Meanwhile, in chicago, pete begins his overnight shift in the newsroom, waiting for police scans to begin their predictable cry. Reporter: There's more than 2,400 shootings so far this year and there's still two weeks left. Covering this beat means you will see more killed in cook county than the battlefield of afghanistan. Reporter: Shot in the back and the arm a couple times. The location is ominous. Reporter: I don't know if kids are on christmas break or whatever, but they're going to find out somebody got shot next to their elementary school. He finds evidence markers. The victim scooped into a car and driven off. Reporter: They're going to transfer him to a trauma center. Waiting there are teams of battle weary doctors and nurses and our david wright. Reporter:11:35 p.M., Rush hour at cook county trauma center. We're going to move you over to this bed, okay? So what happened, man? , man. Yeah, but how many shots? First task for the doctors, counting the bullet holes. One, two -- there's one here. Four. Reporter: He's the victim from the crime scene near the elementary school. And he's clearly in pain. The x-rays show he has more bullets inside him. This guy came in with -- i think we counted a total of 10 or 12 bullet holes. Reporter: Ten? That's a bullet? That's a piece of a bullet, yeah. Reporter: One of them still lodged in his gut, another passed less than an inch from his heart. The question is are we opening his chest or are we opening his belly? You open the wrong cavity and he starts bleeding, you could lose him on the table if you made the wrong choice. Reporter:12:13. Less than an hour after he came into the trauma center, he's in surgery. Major surgery. Whatever went in has to come out. So we have to find the hole on the back side. Reporter: Past 3:00 a.M. By the time they're sewing him up, alive, but not out of the woods yet. Midnight, virginia beach, vi this is one of the seven states that allow guns in bars, so when jessica abbott stops by knuckleheads, she keeps her nine millimeter baretta on her hip. I wanted an extra way to defend myself. Chances are nobody's going to mess with me when I'm open carrying. For some, second amendment rights are grounded in the suspicion of the government. For others, the self-defense urge comes from fear, and these days, it seems there are more sources of fear than ever. If you think that somebody is about to go down, or something is going down, that you can rectify, then you should be able do it. I carry a few different weapons. I just do it to protect myself. I'm not going to have a hassle with a man or get into a fight with an altercation where my children can be in jeopardy if I go down. In houston on that night, that source is facebook. After a mom discovers posts on her son's account discussing a possible shootout at his high school. Responding is lieutenant robert henry. Okay, I'll see you there. He speized in cases potentially involving the mentally ill. You never know on calls like this if they're serious or not. So we take these situations very seriously. What do you have, sir? Police questioned 13 kids over what is probably a hoax, but these days, who knows? Uncertainty brings fear. And back in philly, the parents of that 17-year-old are wrestling with the worst kinds of both. I can't make any promises, okay? What I can tell you is the best hospital in the world for this, okay? They're doing everything they can. There's 15 people work on him right now. While their son was slipping into critical condition, police in this town had taken a gun from a drug dealer. The saying goes, where there's drugs, there's guns. Responded to a woman shot in the back while walking near upscale south street. She's comfort to be in stable condition after being struck in her abdomen. It went in and out of her body. And just before 1:00 a.M., comes word that two 24-year-olds are hit. One of the males is shot in the chest. Extremely critical. They're transporting him temple hospital now. Which one's chest, this one? It may be hard to fathom in places like these, but when we come back, we'll visit those parts of america where happiness is a warm gun. Where families bond at the range and display their passion even in the picture with santa.
This transcript has been automatically generated and may not be 100% accurate.