As a member of the M-19 guerrilla group in the 1980s, Gustavo Petro, who was known as Comandante Aureliano, served 18 months in prison for illegally carrying a firearm. Now mayor of the Colombian capital, Bogotá, Petro is leading an experiment in banning guns from the streets of this city of eight million people, where firearms are part of the backdrop to everyday life.
Bodyguards on high-speed motorbikes whizz through traffic wielding machine guns, security guards at shopping centres pat down customers, and many public buildings have special sand-filled tubes for unloading pistols.
The ban will go into effect from 1 February for three months, and could become permanent if murders drop significantly.
Alvaro Páez, an unarmed doorman at an apartment building in central Bogotá, has seen a few gunfights on his watch and thinks the idea is good, but is sceptical about its results. "There should be limits to walking around with weapons but most crimes are committed with illegal ones so I doubt we'll see much difference," he said.
Under the constitution, Colombians are allowed to own and carry firearms with a licence from the military authorities. But for every one of the two million legally registered weapons in civilian hands, there are four illegal ones, according to a study by the Universidad del Rosario. According to the mayor's office, only 10% of the 1,016 homicides in Bogotá involving firearms last year were committed with registered guns. But a study of similar efforts to ban weapons in other parts of the country between 2009 and 2010 found a "large and significant violence reduction", with homicides dropping an average of 23% and gun injuries 53%.
Petro, who was elected with 32% of the vote but now enjoys a 69% approval rating, is seeking not just a drop in the murder rate but to revolutionise the Colombian attitude to guns.
"It's not just about stopping people who own guns walking around with them. It's part of a policy of laying down weapons, believing in the state's monopoly over weapons and generating a culture of tolerance and love," Petro has said. "Carrying a gun isn't a defence mechanism, it's a risk."
Petro was 17 when he fired his first weapon at a training camp for the M-19 urban guerrilla group. But he and his former comrades in the rebel movement say he was never involved in violence. Instead he was a political leader and ideologue. He worked clandestinely to recruit for M-19 while studying economics at the prestigious Externado University in Bogotá.
In 1985, when Petro was 25, he was captured and tortured for five days. "They beat me every two hours and asked me the same questions again and again," Petro wrote in SOHO magazine. He was serving his 18-month sentence in Bogotá's la Modelo prison when the M-19 besieged the Palace of Justice. More than 100 people, including 11 supreme court judges, were killed when the army retook the building.
The M-19 signed a peace pact with the government in 1990 under which demobilised fighters were granted an amnesty. As part of a political movement born of the peace process, Petro helped rewrite Colombia's constitution and was elected as a representative in congress without abandoning his leftist ideology. In 2006 he was elected senator and gained a reputation as an eloquent speaker and a sharp critic of the then president, Alvaro Uribe. Petro began denouncing in congress the close collaboration between rightwing militias and the political elite, which led to more than 60 politicians, including senators, being arrested. After a failed bid for the presidency in 2010, he helped uncover a widespread corruption scandal that put former mayor Samuel Moreno in jail.
Following Petro's announcement of the experimental weapons ban, which received military approval, the government of President Juan Manuel Santos said it would legislate to tighten restrictions gun ownership nationwide.
