A gunman shot several people outside the Empire State Building today. Before police officers killed the suspect, ten people were shot, one fatally. Some victims may have been wounded by police officers attempting to stop the shooter.

Police are still unraveling details about the shooting, but the New York Times reported that the suspect, Jeffery Johnson, was laid off last year from his job as a clothing designer. According to Police Commissioner Raymond W. Kelly, the suspect apparently shot and killed his former co-worker outside the apparel importer where they worked. He then walked down the street to the front of the Empire State Building and opened fire on people standing there. Johnson was found carrying a .45-caliber semiautomatic handgun.

This is just the latest of a series of violent, unexpected attacks by gunmen this summer. Each time we struggle to understand why and what we should do. Tragedies involving gun violence always renew the discussion on whether concealed carry laws give citizens the means to prevent deaths or hand killers the tools they need. Would stricter gun control choke violence at its roots? It is hard to say.

A recent graphic on our Web site shows that the average number of guns per owner has increased and that more states have laws that allow concealed weapons. Those trends are not conclusive evidence, but they do fuel debate.

In a post shortly after the Aurora, Colo., shooting in July, Eric Michael Johnson, a doctoral student in the history of science at University of British Columbia and a Scientific American blogger, explained that "[of] the 34 countries in the Organisation for Economic Co-operation and Development (OECD), the U.S. ranks fifth in homicides just behind Brazil (highest), Mexico, Russia, and Estonia. Our nation also holds the dubious honor of being responsible for half of the worst mass shootings in the last 30 years."

Johnson examined and dismissed several possible causes, including whether the U.S.'s grim gun violence statistics are the result of a culture that "fetishizes violence" or whether the sheer number of guns increases the number of homicides. He concludes, however, that income inequality may explain high homicide rates. If so, then we might be able to tackle violence at its source:

"The high level of inequality, both within the United States as well as between countries globally, was constructed through a process of social interactions. It can be deconstructed the same way. If the interpretation from social capital is correct, it suggests that building relationships through our schools, labor unions, farmers’ markets, and gun ranges, at City Hall and the State House, or active participation in our churches, temples, and mosques, can ultimately make us all more secure. But at the same time it means collectively challenging the policies of those high-ranking members in our society whose obsession with status leaves the rest of us completely stressed out."

Harvard University social scientist Steven Pinker argued in a data-rich book published last year that violence overall has declined. Paralleling Johnson's argument, Pinker cited a "culture of dignity" as the cause. As the nation is buffeted yet again by a senseless attack, take some heart that pulling together could set us on a more peaceful path.