Distinctive factors contribute to the high rates of violent crime in Latin America. Many countries in the region had recent civil wars, resulting in a large number of weapons in circulation. Drug- and gang-related violence is widespread. “It’s dangerous to make too tight a link between the availability of weapons and homicide rates,” said Jeremy McDermott, a co-director of InSight Crime who is based in Medellín, Colombia. “There are lots of other variables.”

Still, he said that the recent sharp increase in homicides in Venezuela could be in part explained by the abundance of arms there. Although the government last spring imposed a one-year ban on importing weapons, there had previously been a plentiful influx from Russia. There is a Kalashnikov plant in the country.

In 2011, according to the United Nations Office on Drugs and Crime, Honduras led the world in homicides, with 91.6 per 100,000 people. But rates were also alarmingly high in El Salvador (69.1), Jamaica (40.9), Colombia (31.4) and Guatemala (38.5). Venezuela’s was 45.1 in 2010 but is expected to be close to to 80 this year. The United States’ rate is about 5.

THOUGH many of these countries have restrictions on gun ownership, enforcement is lax. According to research by Flacso, the Guatemalan Social Science Academy, illegal guns far outnumber legal weapons in Central America.

All that has spawned a thriving security industry — the good guys with guns that grace every street corner — though experts say it is often unclear if their presence is making crime better or worse. In many countries, the armed guards have only six weeks of training.

Guatemala, with approximately 20,000 police officers, has 41,000 registered private security guards and an estimated 80,000 who are working without authorization. “To put people with guns who are not accountable or trained in places where there are lots of innocent people is just dangerous,” Ms. Peters said, noting that lethal force is used to deter minor crimes like shoplifting.

Indeed, even as some Americans propose expanding our gun culture into elementary schools, some Latin American cities are trying to rein in theirs. Bogotá’s new mayor, Gustavo Petro, has forbidden residents to carry weapons on streets, in cars or in any public space since last February, and the murder rate has dropped 50 percent to a 27-year low. He said, “Guns are not a defense, they are a risk.”