Is there a divide between Clayton and Branas? Yes, but perhaps not exactly the one you'd predict. And there are areas of agreement, too. For instance, both believe gun owners are often unfairly vilified. And they share limited faith in the value of background checks that can only block attempts at lawful gun purchases.
"Nobody wanted those kids to die," Clayton says. But he sees no need for new national legislation: "Why do I have to give up my rights because someone who shouldn't have gotten a gun had one?"
Clayton contends that the expired ban on assault rifles and high-capacity magazines had little effect, and says New Jersey's stricter gun laws show that laws do little to stop crime. "Have you been to Camden lately?" he asks.
Background checks? "We don't oppose them," he says. He's been performing them for more than a decade under a state law that requires gun sellers to perform checks, at least for handguns, even if they sell firearms at gun shows - a major loophole in some parts of the country.
"The system does work. If you come in here and 30-some years ago you had an assault on your record, you're not going to be able to buy a gun," says Clayton, who runs the store and its firing range with his wife, Sharon, and their son, Tom Jr. Pennsylvania law requires even private sellers to perform the checks for handguns, so Clayton often does them for his customers.
One obvious limitation is that mental-health records are only good for flagging people with conditions that have already drawn legal scrutiny, such as through involuntary commitment. To Branas and others concerned about privacy rights, that reflects a justifiable balance.
"It's been difficult to connect mental illness with the perpetration of violence," he says. "You don't want to exacerbate the stigma of seeking mental-health care. And you don't want to violate patient confidentiality."
That doesn't mean Branas is satisfied with the status quo - 100,000 shootings a year in the United States, and nearly a third of them fatal. Far from it.
As an epidemiologist who focuses on how environments affect health and well-being, Branas has long been interested in interventions - including nontraditional ones, such as blight reduction - that might reduce violence. And he coauthored a 2009 study that examined - and failed to support - one of Clayton's core beliefs: that carrying a gun makes him safer.
Clayton says gun ownership is about protecting home and family. "You know what the police are there for? To come take the report," he says. "You think they're going to stop somebody from coming into your house?"
Branas, whose study prompted Congress to expand 1990s restrictions on using federal dollars "to advocate or promote gun control," says gun-rights advocates miss the point of research such as his. It's not aimed at blocking gun ownership. It's aimed at reducing harm, such as from the rural gun suicides that actually occur at higher rates than urban gun homicides.
Branas says mass slayings often end in the killer's suicide, a phenomenon that merits closer attention. So do interventions that focus on alcohol's role in gun violence. We need more and better evidence, not the reduced rate of research that resulted from chilling federal restrictions.
"We're not talking about eliminating guns," he says. "These are part of people's families. These are part of people's cultures. We're going to have to learn how to live healthy lives with those firearms."
Contact Jeff Gelles at 215-854-2776 or email@example.com. Follow him on Twitter at @jeffgelles.