The two thoroughbreds sprinted down a country track, a few million dollars in the bettors' kitty and an old-fashioned camera waiting at the finish line.
When the race was over, as veterinarians guided the expensive equines back to their air-conditioned trailers, gamblers at the private track began to argue over the nose-to-nose conclusion. Among them were members of a band of hit men known as the Zetas, employees of the Gulf cartel of drug traffickers.
Let's just wait for the film to be developed, someone said.
Then, above the din, another voice rang out. "I've come to kill you!"
A new chapter was being added to the violent saga of Mexico's most notorious drug ring. More than a dozen people may have been killed in the gunfire that followed, an ambush in which the hit men appear to have attacked one another.
The Zetas were Mexico's first drug cartel army, and in many ways they and their employers are responsible for the militarization of the country's drug conflict. President Felipe Calderon deployed the national army this year to fight traffickers in several Mexican states.
The March shootout at the Villarin track was one of many bloody episodes in what appears to be an escalating power struggle within the Gulf cartel. Experts say the increase in tension was triggered by the January deportation of reputed cartel leader Osiel Cardenas to face trafficking charges in the U.S.
"The cartel has split," Genaro Garcia Luna, public security minister and Mexico's top cop, said last week. "This has generated a new wave of violence as they fight over the regions Osiel controlled."
The cartel, based in the border state of Tamaulipas, grew wealthy and powerful thanks to the U.S. appetite for Colombian cocaine, and both of its branches remain potent forces in Mexico. Almost every week, a new act of cruelty, boldness or stupidity by the Zetas plays out in the country's tabloids and newscasts.
Before the 1990s, groups based in the Pacific Coast state of Sinaloa dominated Mexico's drug trade. The country's traffickers were becoming cash-rich as Colombian cartels increasingly ceded key smuggling routes into the U.S. to them.
To challenge the dominance of the Sinaloans, the ascendant Gulf cartel began recruiting soldiers from the army. The Zetas were born.
Their founder was a former army officer who had deserted: Lt. Arturo Guzman Decena, known as Zeta 1. He reportedly received training from the Israeli military.
According to the attorney general's office, Guzman is believed to have recruited several soldiers from his paratrooper brigade and at least 40 former members of the Mexican special forces.
"They brought the ideas of counterinsurgency and psychological warfare to the drug business," said Luis Astorga, an expert on the industry. "The idea is that if you paralyze your adversaries with fear, you've won half the battle."
The Zetas' mission was to wrest from Sinaloa and other groups the Gulf cartel's "right" to smuggle drugs through a given port or border city.
"The drug world is like any other business," Astorga said. "You try to take territory and profits from your rivals. But there are no courts to settle disputes. There is only violence."
The Gulf traffickers took advantage of the low pay and high desertion rate of the Mexican army, where one in eight soldiers deserts every year. Cartel members reportedly enticed the troops with large sums of cash and positions of responsibility, something the Sinaloa traffickers still shy away from.
"With the Sinaloa group, family ties have always been important," Astorga said. "To them, bringing in soldiers and giving them power was like admitting a Trojan horse into the fold."
Raul Benitez, a Mexico security expert at American University in Washington, says the Gulf cartel valued the army veterans for their knowledge of weapons and explosives. (In Mexico, the army regulates all firearms.)
As the Zetas gained strength, they brought increasingly powerful weaponry into the drug war, including .50-caliber machine guns originally designed as antiaircraft weapons. In recent years, grenade attacks on police stations have become common.
In popular legend, the Zetas are gunslingers with bazookas and military experience. They pull off killings that suggest a certain level of tactical training: In February, for example, they donned army uniforms to enter two Acapulco police stations and kill seven officers and employees.
But like many legends, the Zeta myth is built around a core truth that fades deeper into history each year.
Guzman -- Zeta 1 -- was killed in 2002 in a shootout with the army in Matamoros. As many of the other original hit men fell, the cartel sought new firepower, first recruiting members of the Guatemalan special forces, the Kaibiles.
Many of the original Zetas are dead or in prison, Mexican authorities say. U.S. officials say current members probably were recruited from the ranks of Mexico's urban and rural poor.
"It's gotten to the point where you get drunk, shoot at some cans and paint your face black, and that makes you a Zeta," said a U.S. official who asked not to be named. "A lot of it is image and myth."
"They are young people between 25 and 30 years old," said Garcia Luna, the public security minister, adding that the recruits are drawn by the aura of wealth and power surrounding the Zetas. "If you look at them face to face, you can see who they really are: people of lower social status and poor education."
In the racetrack shootout, the number and names of those killed remain a mystery, like much about the Zetas.
According to news reports, at least one high-ranking hit man died: Efrain Torres, also known as Zeta 14 or the Spark. Federal authorities say one other man was killed. But his name is a state secret and won't be released until 2019.
Residents say the Zetas may have secretly buried as many as a dozen other men.
After the shootout, attacks and counterattacks spread throughout Veracruz state. A police chief was killed. Several journalists and government officials were accused of being Zeta collaborators and went into hiding. Someone dumped a severed head at a newspaper office.
The violence even reached a cemetery 100 miles away.
"They tied up the guard, broke through a few layers of concrete and pulled out the coffin," said Raul Vargas, director of a funeral home and cemetery in the town of Poza Rica, describing how men believed to be Zetas stole the corpse of the recently buried Zeta 14.
"This was one of our deluxe coffins, so it was pretty heavy. They loaded it on a truck and then they were gone."
The escalating violence has gone beyond internal strife. In recent weeks, Zetas and the Gulf cartel have been linked to slayings in Sonora, Guerrero, Michoacan and other states. In some cases, the Zetas have been the victims of gruesome attacks.
In March, a half-naked man with a Z painted on his stomach was videotaped while being tortured and interrogated by unidentified captors. On tape, the man confesses to his role in the Acapulco police killings. In video posted and then quickly removed from YouTube, he is strangled and decapitated.
The tape is one of dozens of "narco messages" that have surfaced as the drug cartels wage propaganda wars against one another and the authorities.
The messages usually take the form of notes left next to corpses. Often they are attempts to spread disinformation, analysts say. They may name government and police officials as being the accomplices of rival cartels, creating the sense that anyone and everyone is tainted by drug corruption.
One such message aired in March on the Azteca television network, three weeks after the racetrack shootout. In a videotape, two alleged Zetas from Veracruz confess to their unseen captors that they committed a series of crimes, including 23 killings. A local police chief was killed, one says, because he failed to prevent federal police from arresting Zetas wounded in the shootout "even though he knew he was getting money from the cartel."
A newspaper editor was killed, one man says, "because he wrote a lot of things against the cartel, affecting our relationship with the authorities."
The tape names two columnists, including one from the newspaper Notiver, as paid Zeta collaborators. In the newsroom, a reporter called that allegation pure fiction.
"I know those two people, and they live ordinary lives," said the reporter, who asked not to be named. The reporter sees the missive as an attempt to spread fear and confusion.
"There's a collective psychosis because every night there are new reports of attacks," the reporter said. "This kind of drug war is something we've never seen in Veracruz before."
About 20 more people have been killed in Veracruz since the racetrack shooting.
All along the Gulf Coast, in the small towns where they commonly operate, the cartel's gunmen remain as conspicuous as an invading army. The residents learned quickly never to stare, despite the gold-plated rifles the men carry and the late-model SUVs they drive.
In Coatzacoalcos, 130 miles south of Veracruz, a newspaper photographer encountered five armed men on the street one day in March as they were being detained by police. The suspects had military-style haircuts, machine guns and designer shoes, said the photographer, who asked not to be named.
They seemed unfazed by their detention, telling the officers, "You probably just better let us go now before this problem gets more serious."
Only later did the photographer realize what had happened. He had looked into the faces of some of Mexico's most dangerous men and lived to tell the tale.
Carlos Martinez of The Times' Mexico City Bureau contributed to this report.