Twenty seconds of shooting, 432 bullets, five dead policemen.
Four of the corpses are sprawled over a shiny-new Dodge Ram pick-up truck that has been pierced so many times it resembles a cheese-grater. The bodies are contorted in the unnatural poses of the dead – arms arched over spines, legs spread out sideways.
The fifth man is a moustached 48-year-old lying 10 feet from the pick-up, bathed in his own blood. His eyes are wide open, his right hand stretched upward clasping a 9-mm pistol – a death pose that could have been set up for a Hollywood movie.
It is a balmy evening in Culiacan, Sinaloa, near Mexico's Pacific coast. The policemen had stopped at a red light when the gunmen attacked, shooting from the side and back, unleashing bullets in split seconds. A customised Kalashnikov can unload 100 rounds in 10 seconds. This is a lightning war.
I arrive 10 minutes after the shooting and a crowd of onlookers is already thickening. "That one is a Kalashnikov bullet. That one is from an AR15," says a skinny kid in a baseball cap, pointing at a long silvery shell next to a shorter gold one.
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Besides them, middle-aged couples, old men and mothers with small children gawk at the morbid display. The local press corps huddles together, checking photos on their viewfinders to ensure they have the best images. They are relaxed, cheery; this is their daily bread.
A battered Ford Focus speeds through the crowd. The wife of one of the victims jumps out and starts screaming hysterically. Her swinging arms are held back by her brother, his eyes red with tears. It is only when I see the pained look on their faces that the loss of human life really sinks in.
Anyone with half an eye on the news knows that Mexico is in the midst of a drugs war, with rival cartels battling for control of a $30 billion trade with the United States. The country so deep in blood it is getting harder to shock the locals. Even the kidnapping and killing of nine policemen, or a pile of craniums in a town plaza, isn't big news.
Only the most sensational atrocities now grab media attention: a grenade attack on revellers celebrating independence day; the sewing of a murder victim's face onto a football; an old silver mine filled with 56 decaying corpses, some of the victims thrown in alive.
In the five years of President Felipe Calderon's administration, the government admitted earlier this month, the drug war has claimed 47,500 lives including those of 3,000 public servants – policemen, soldiers, judges, mayors, and dozens of federal officials.
Such a murder rate compares to the most lethal insurgent forces in the world – and is certainly more deadly than Hamas, ETA, or the Irish Republican Army in its entire three decades of armed struggle.
The nature of the attacks is even more intimidating. Mexican gangsters regularly shower police stations with bullets and rocket-propelled grenades; they carry out mass kidnappings of officers and leave their mutilated bodies on public display; they even kidnapped one mayor, tied him up, and stoned him to death on a main street.
I originally travelled to Latin America with the goal to be a foreign correspondent in exotic climes. The Oliver Stone film Salvador inspired me with its story of reporters dodging bullets in the Central American civil wars. But by the turn of millennium, the days of military dictators and communist insurgents were no more. We were now, apparently, in a golden age of democracy and free trade.
I arrived in Mexico in 2000 the day before former Coca Cola executive President Vicente Fox was sworn into office, ending 71 years of rule by the Institutional Revolutionary Party.
This was a titanic moment in Mexican history, a seismic shift in its political plates, a time of optimism and celebration. The clique who ravaged the country and lined their pockets for most of the twentieth century had fallen from power.
In the first years of the decade, no one saw the crisis ahead. The American media heaped high expectations on the cowboy-boot wearing Fox as he entertained Koffi Annan and became the first Mexican to address a joint US session of Congress. The first wave of serious cartel warfare began in the autumn of 2004 on the border with Texas and spread across the country. When President Felipe Calderon took power in 2006 and declared war on these gangs, the violence multiplied overnight.
The same system that promised Mexico hope was weak in controlling the most powerful mafias on the continent. The old regime could manage organised crime by taking down a token few gangsters and taxing the rest. Mexico's drug war is inextricably linked to the democratic transition.
Its special-force soldiers became mercenaries for gangsters. Businessmen who used to pay off corrupt officials had to pay off mobsters. Police forces turned on one another – sometimes breaking into shoot-outs.
Following the rise of the Mexican drug cartels has been a surreal – and tragic – journey. I have stumbled up mountains where drugs are born as pretty flowers; dined with lawyers who represent the biggest capos on the planet; and I got drunk with American undercover agents who infiltrate the cartels. I also sped through city streets to see too many bleeding corpses – and heard the words of too many mothers who had lost their sons, and with them their hearts.
I have met the assassins, too; men like Jose Antonio from Ciudad Juarez, probably the most murderous city on the planet – just seven miles from the border with the US. Jose stands at just five feet six and has chocolate coloured skin, earning the nickname "frijol" or bean. He has a mop of black curly hair and bad acne, like many 17-year-olds. But despite his harmless demeanour, he has seen more killings than many soldiers serving in Iraq and Afghanistan.
Frijol came of age in a warzone. When Mexico's two most powerful cartels, the Zetas and Sinaloa Cartel, began fighting in 2004, he was just 12 – and joined a street gang in his slum. At 14, he was already involved in armed robberies, drug dealing and regular gun battles with rival gangs.
At 16, police nabbed him for possession of a small arsenal of weapons – including two automatic rifles and an Uzi – and being an accessory to a drug-related murder.
Frijol is typical of thousands of teenagers and young men. His parents hail from a country village but joined the wave of immigrants that flocked to work in Juarez, sweating on production lines making consumer goods for an average of $6 a day.
It was a radical change in their lives. Frijol's parents still celebrated peasant folk days and macho country values. But he grew up in a sprawling city of 1.3 million where he could tune into American TV channels and see the skyscrapers of El Paso over the river. Contraband goods and guns flooded south and drugs went north. He was in between markets and in between worlds.
While Frijol's parents slaved in the factories, he was left for hours at home alone. He soon found company by joining one of Juarez's street gangs - known as barrios, the very word for neighbourhood. His was the "Calaberas", or skulls, and had 100 members.
"The gang becomes like your home, your family. It is where you find friendship and people to talk to. It is where you feel part of something. And you know the gang will back you up if you are in trouble."
Frijol learned to use guns in the Calaberas. Arms moved around Juarez streets freely and every barrio had its arsenal. "Men with connections started looking at who knew how to shoot," explains Frijol. "There was a guy who had been in the barrio a few years before and was now working with the big people.
He started offering jobs to the youngsters. The first jobs were just as lookouts or guarding tienditas [little drug shops]. Then they started paying people to do the big jobs... to kill."
I ask how much the mafia pays to carry out murders. Frijol tells me without stopping for a moment. One thousand pesos. That is about $85.
The figure seems so ludicrous that I check it out in other interviews up in the barrios with former and active gang members. They all say the same thing. One thousand pesos to carry out a killing. The price of a human life in Juarez is just $85.
To traffic drugs is no huge step to the dark side. All kinds of people over the world move narcotics and don't feel they crossed a red line. But to take a human life - that is a hard crime. I can at least comprehend assassins killing to jump from poverty to riches. But for someone to take a life for $85 – enough to eat some tacos and buy a few beers over the week – shows a terrifying degradation in society.
I ask Frijol what it is like to be in fire fights, to see your friends dead on the street and to be an accessory to a murder. He answers unblinking. "Being in shootouts is pure adrenalin. But you see dead bodies and you feel nothing. There is killing every day. Some days there are 10 executions, others days there are 30. It is just normal now."
I speak to psychologist Elizabeth Villegas. The teenagers she works with have murdered and raped. I ask, how does this hurt them psychologically? She stares back at me as if she hasn't thought about it before.
"They just don't understand the pain that they have caused others," she replies. "Most come from broken families. They don't recognise rules or limits."
The teenage sicarios know that under Mexican law, minors can only be sentenced to a maximum of five years in prison no matter how many murders, kidnappings or rapes they have committed. Many convicted killers will be back on the streets before they turn 20. Frijol himself will be out when he is 19.
But the law is the least of their worries; the mafias administer their own justice. Juarez Cartel gunmen went to neighbourhoods where gang members had been recruited for the Sinaloans; a death sentence was passed on the whole barrio. The Sinaloan mafia returned the favour on barrios that had joined the Juarez Cartel.
I went to a neighbourhood where 20 teenagers and young men had hung out on a street corner a year ago. Fifteen had since been gunned down, a bar they hung out in torched.
A few of the survivors are incarcerated, the rest have fled, leaving a neighbourhood looking like a ghost town.
Frijol recognises that youth prison may be hard. But it is a lot safer there than on the streets now. "I keep hearing about friends who have been killed out there. Maybe I would be dead too. Prison could have saved my life."
On the streets of Mexico, death was never far away. Five sources whose interviews helped shaped my book were subsequently murdered or disappeared – although these killings almost certainly have nothing to do with my work.
One of them, Honduran anti-drug chief Julian Aristides Gonzalez, gave me an interview in his office in the sweaty Honduran capital. The square-jawed officer chatted for several hours about the growth of Mexican drug gangs in Central America and the Colombians who provide them with narcotics.
In his office were 140 kilos of seized cocaine and piles of maps and photographs showing clandestine landing strips and narco mansions. I was impressed by how open and frank Gonzalez was about his investigations and the political corruption they showed up.
Four days later, he gave a press conference showing his latest discoveries. Next day he dropped his seven-year old daughter off at school. Assassins drove past on a motorcycle and fired 11 bullets into him. It turned out he had planned to retire in two months and move his family to Canada.
*El Narco: The Bloody Rise of Mexican Drug Cartels by Ioan Grillo (Bloomsbury, £12.99), is available from Telegraph Books at £11.99 + £1.25