MEXICO CITY - It was Easter weekend, and the Almanza family was heading to the beach the day little Martin and Brayan died in a hail of gunfire and grenade explosions.

The family's Chevrolet Tahoe was stuffed with relatives. The eight adults in the front laughed at a DVD of stand-up comedy. The five kids giggled in the back, flopped atop coolers and blankets.

"Everybody was excited - we were ready for the beach," said Martin Almanza Sr., who was driving.

On the road ahead, Almanza saw a convoy of army trucks on the shoulder of the road, a common sight in Mexico, where soldiers have been leading a battle against drug cartels since 2006.

What happened next - a flash of explosions and gunshots, shredding metal and flying glass - has ignited allegations of a military cover-up and highlighted a snowballing record of abuses by Mexican soldiers. It comes as the U.S. government is deciding whether it should withhold millions of dollars in aid to fight drug trafficking because of alleged human-rights violations.

The Defense Ministry says the Almanzas stumbled into a firefight between soldiers and drug smugglers.

But investigators with Mexico's National Human Rights Commission, a government body charged with investigating complaints against federal agencies, say soldiers opened fire on the Tahoe unprovoked, possibly out of panic, then brought in vehicles, weapons and cadavers to make it look like a two-way gunfight.

No one argues about the aftermath: By the time the shooting stopped, 9-year-old Martin was dead, his little body slumped next to a gaping hole left by a grenade in the back of the Tahoe.

Brayan, 5, lay dead in his mother's arms from a bullet in the back of his head. Six other relatives were wounded.

It was April 3, Holy Saturday.

War gone amok

For this report, The Arizona Republic interviewed Almanza family members, investigators, lawyers involved in the case and an officer with Mexico's Defense Ministry who is familiar with the army's investigation.

The Republic reviewed three publicly released reports on the shooting and also allowed to view investigative files, photographs and other documents that are normally secret under Mexican law.

Together, they give a glimpse inside an increasingly chaotic drug war, with an army ill-suited for police work and civilians at risk nearly four years after President Felipe Calder�n launched his military crackdown on drug cartels. Since then at least 21,000 people have died in drug-related violence.

As the number of troops working full time on anti-drug missions has grown from 10,000 to 45,000, complaints of abuse by soldiers have shot up eightfold, from 206 in 2006 to 1,833 last year.

With violations piling up, rights groups are urging the U.S. State Department to withhold some $67.5 million in anti-drug aid this year.

The army's version

The Mexican Army and the Almanza family have given dramatically different accounts of what happened that evening on Mexico's Highway 2, about 75 miles east of Nuevo Laredo.

They disagree over the time of the clash, whether there was enough daylight for the soldiers to tell if the Almanzas were civilians or combatants, and - most importantly - whether the Tahoe was alone on the dangerous highway.

The Almanzas had left their home in Nuevo Laredo and were heading east along the Rio Grande toward Matamoros, a drive of about 3�1/2 hours.

Soldiers in the area were already on high alert that day, according to the Defense Ministry's report of the shooting.

A tipster had reported a shootout between drug gangs on the highway between Ciudad Mier and New Ciudad Guerrero, a hotbed of violence close to the Mexico-Texas border.

Within minutes, soldiers from Urban Mobile Unit B arrived at the scene. Six bullet-riddled sport-utility vehicles sat beside the road, and weapons were scattered all around.

The soldiers rolled northward, guns at the ready, to look for smugglers fleeing the gunfight. It was between 8 and 8:30 p.m., the military says - long after dark.

As the troops turned west along the shore of the Falcon Reservoir, seven vehicles appeared out of the darkness, the military says. Bullets ripped toward the soldiers.

The soldiers returned fire, blinded by the headlights. Four of the vehicles fled.

Finally the shooting stopped, the military says, and the soldiers approached the three remaining vehicles: a blue Dodge pickup, a red Hummer and, in the middle, a black Chevrolet Tahoe.

In the pickup, they found a dead man in camouflage fatigues. The Hummer held a second body, also in fatigues.

In the Tahoe, Carlos Rangel, the Almanza boys' uncle, sat alone, his legs pierced by bullets.

Then the soldiers made a chilling discovery: A boy lay dead in the back of the Tahoe.

The family's version

The Almanza family says there were no other vehicles around them and no attack on the soldiers.

The attack happened when it was still light out, and the military pickups were parked on the other side of the road, not moving, family members told The Republic.

As the Tahoe approached, Martin Sr. slowed down and rolled down his window. A soldier gestured for them to continue, and the Tahoe rolled on, he said.

Seconds later, gunfire tore through the back window of the pickup.

Martin swerved off the road and slammed to a stop. A bullet had pierced his hand, and he was bleeding heavily. In the back seat, bullets had torn through Carlos' legs. His pants were soaked with blood.

Cynthia Salazar, Martin's wife, said she grabbed a towel in her lap and stumbled out of the passenger-side door waving it.

"I screamed at them not to shoot, that we were a family, but they didn't hear me," she said. "I shouted, 'Martin, Martin get out! You've got to help me with the kids. We've got to save the kids!' "

As gunfire battered the back of the Tahoe, the family pulled their children out.

As Cynthia picked up Brayan, a bullet cut through her abdomen. Brayan went limp in her arms. Martin Sr. grabbed the boy with his good arm.

The family fled into the bushes, but Cynthia suddenly realized Martin Jr. and Carlos were not with them. Going back to the Tahoe, she could see the boy's green shirt with black stripes in the back of the vehicle.

As she reached out, she said, a grenade exploded near her. Frightened, she backed away.

"Carlos was still in the truck alive, and he shouted at me not to leave him," she said. "I told him if I stayed they were going to kill me, because they wouldn't stop shooting."

The 10 relatives fled into the bushes with Brayan's lifeless body, leaving Carlos and Martin Jr. behind. Eventually they made it to a nearby ranch, where they called for help.

Back in the Tahoe, Carlos sat bent over, unable to move his legs. There was no sound from the boy behind him.

The shooting stopped. Carlos said the soldiers approached him and one put a rifle to his head.

"Another one said, 'Just kill him. He's going to die anyway,' " Carlos said.

Suddenly, a commander told the soldiers to stop. They had discovered Martin's body in the back of the truck.

A cover-up?

In a 1,400-page report released June 16, the National Human Rights Commission issued its most damning accusation in four years of Calder�n's crackdown.

"The death of the minors Brayan and Martin Almanza Salazar and the wounds suffered by (the other victims) were caused by the direct and discretional fire from members of the Mexican Army, and not crossfire with members of organized crime," the report said.

It also accused the soldiers of "manipulations to misdirect the investigations," citing bullet holes that conflicted with the army's account, witnesses who said they only saw one vehicle immediately after the shooting, and hospital admission records that indicated the shooting happened when it was still light out.

"In the victims' versions of events, everything fit together perfectly," said Marat Paredes, head of the commission's investigations involving the police and military. "The (defense ministry's) official version, to be honest, does not add up in absolutely any way."

The soldiers may have simply panicked, said Raymundo Ramos, a lawyer who is representing the family. The vehicle had foreign plates, he said, because Almanza, who imports used cars for a living, had just bought it in Texas two weeks before.

"The Mexican army has been at war for three years, and they're under a lot of pressure," Ramos said. "I think (the soldiers) got confused. They saw this vehicle go by, and because of the type of vehicle and all the people they saw inside it, they started shooting."

To cover up their mistake, the soldiers likely drove two other vehicles, the two cadavers and some weapons from the scene of the earlier gunbattle between cartels, Ramos said. That site was only about 5 miles away.

Army's defense

The Defense Ministry did not respond to requests for an on-the-record interview.

But in a rare news conference shortly after the shooting, the then-head of military justice, Gen. Jos� Ch�vez, said the military's account is supported by two identical statements signed by Cynthia Salazar on April 4 when she went to the police stations in Ciudad Mier and Ciudad Madero to pick up her sons' bodies.

Those statements say Salazar saw six SUVs pass the family on the highway shortly before the Tahoe met the army trucks.

Salazar denies she ever told detectives that. She says she cannot read, and she says the detectives never read her the text of her statement and would not hand over the bodies until she signed it.

Paredes said it is suspicious that the two statements are identical, even though they were supposedly taken by two different detectives in two different cities.

The National Human Rights Commission urged the military to punish the soldiers, compensate the family and review its rules of engagement. But under Mexican law, its recommendations are not binding, and civilian prosecutors have no authority over soldiers who commit offenses while on duty.

The findings attracted intense attention in Mexico and abroad. Television stations showed animated graphics of the shooting. London-based Amnesty International and New York-based Human Rights Watch urged the military to hand over the case to civilian authorities.

Martin Sr. and Cynthia were invited to the presidential mansion in Mexico City, where President Calder�n promised them a full investigation.

But nearly five months later, the defense ministry says it is still investigating and has not reached a conclusion in the case.

No soldiers have been disciplined, the ministry says.

Broader issue

The Almanza killings and their alleged cover-up reflect an emerging pattern, with soldiers acting illegally and then trying to hide the evidence, said Nik Steinberg, an analyst for Latin America at Human Rights Watch.

"What these cases really lay bare is the fact that the military in certain cases is willing to distort evidence or is willing to not share other evidence in order to protect its own (soldiers)," Steinberg said.

The military has only convicted seven soldiers of wrongdoing since 2006, despite 59 cases of major civil-rights violations - usually involving death, rape or torture - confirmed by the National Human Rights Commission.

In 2007 the army was found responsible in only seven of these major cases. By 2009, that number was 30 - nearly four times as many as any other government agency. Twenty-eight of the 30 cases in 2009 involved torture.

Like the Almanza case, there have been at least five other shootings of unarmed civilians along roads or at highway checkpoints. They include a June 2007 attack in which drunken soldiers sprayed an SUV with gunfire in Sinaloa state, killing two women and three children ages 6, 3 and 1.

In many cases, the military has tried to cover up killings, the National Human Rights Commission says. In another case that attracted national attention, this month it accused soldiers of planting weapons on two university graduate students caught up in a shootout in Monterrey on March 19.

President Calder�n says soldiers must respect human rights, but he also has warned against sending troops into battle "with their hands tied behind their back." On Aug. 19 he told legislators that soldiers should not be expected to hold their fire until attacked.

"When facing gangs that use rocket launchers . . . we cannot leave our troops at the mercy of the violent and destructive nature of the criminals," Calder�n said.

Amnesty International and Human Rights Watch have urged the United States to withhold part of its aid to Mexico, saying the military has violated the conditions of the Merida Initiative, the three-year, $1.3. billion aid package that the United States pledged in 2007 to help Mexico fight cartels.

Under the terms of the package, the United States is supposed to withhold 15 percent of the money unless Mexico ensures that civilian authorities investigate and prosecute all claims of human-rights violations by soldiers, among other requirements. The rules were written by Sen. Patrick Leahy, D-Vt., chairman of the budget subcommittee overseeing U.S. foreign aid.

In 2008 and 2009, the U.S. State Department spent the money anyway. This year Congress has earmarked $450 million for Mexico, with $67.5 million dependent on Mexico's human-rights record.

Tim Rieser, an aide to Leahy, said new language in a budget bill passed in June should clarify that Mexico must meet the human-rights requirements before the State Department can spend the 15 percent.

"The situation in Mexico is very troubling," Rieser said. "Reports of human-rights abuses committed by the armed forces have increased."

For rights activists, the Almanza case is a key test of Mexico's justice system, said Kerrie Howard, deputy director for the Americas at Amnesty International.

"This was more than just a mistake," Howard said. "The (human rights commission) highlighted deliberate fabrication of evidence. The United States needs to be concerned."

Reach the reporter at chris.hawley@arizonarepublic.com.