MEXICO CITY -- The Almanzas slowed down as they drove their black pickup past what they believed to be an army checkpoint in violent northeast Mexico. They rolled down their windows, they say, so the soldiers could see they were a family. But the masked men in uniform instead opened fire, and two Almanza children, aged 9 and 5, were killed.
Fifteen days earlier and just 100 miles away, two promising university students were killed at the gates of their school during an army battle with drug traffickers. The army initially identified the pair as shooters but later retracted the claim after the victims' families came forward.
As the Mexican government's war against drug cartels increasingly claims the lives of innocents, the handling of the two cases is being closely watched.
In the past week, the army has sought to exonerate itself in both. Three of the four victims were found to have been killed by drug traffickers and not soldiers, the army and the attorney general's office said as they released the results of investigations conducted by these same authorities. (The killer of the fourth victim -- one of the university students -- was not identified.)
Families of the victims decried the results as whitewashes. The situation casts a spotlight on what human rights activists say is one of the most troubling aspects of the military's conduct of the drug war -- that the army is allowed to investigate itself in cases involving questionable tactics. In both these cases, the national government, under international and domestic pressure, has sought to inject civilian authorities into the investigative process. But issues of credibility remain.
In the deaths of the Almanza children, the gunmen at the checkpoint were not soldiers at all but drug traffickers fighting each other to control the disputed road from Nuevo Laredo to Reynosa, according to Jose Luis Chavez Garcia, head of the military justice office. The traffickers opened fire first on the Almanzas, then engaged a military patrol that approached, Chavez said.
"Pure lies," Cynthia Salazar, mother of the two children killed at the checkpoint, said in an interview after the report of the army-led investigation was released.
She recalled holding her 5-year-old, Brian, in her lap on that April 3 afternoon as the family traveled to the beach from their home in Nuevo Laredo, near the border with Texas. It was Easter weekend. The truck was packed with seven children between the ages of 3 months and 11 years, two adult males and three women.
"We've gotten used to army checkpoints," Salazar, 28, said. "We know how they are and the precautions to take."
After their vehicle moved slowly, windows down, past what Salazar described as four truckloads of masked soldiers, shots rang out. According to Salazar, the soldiers opened fire on her family, shooting out the tires of their truck and continuing to shoot and then toss grenades at them even as they begged for mercy and tried to escape toward the roadside hills.
A bullet pierced Salazar's stomach, she said, and the same bullet killed Brian. Nine-year-old Martin was also killed, and Salazar's husband, Martin Almanza, was wounded.
While the army led the investigation of the incident, it said civilian prosecutors were also involved, and, in conclusions released late last week, disputed Salazar's version of what happened.
Grenades used by the traffickers hit the back of the Almanza truck and killed the two children, Chavez said. He acknowledged gunfire from the army strafed the front of the vehicle. But he added that the military-grade grenades were of a caliber that the Mexican army does not possess.
A major problem, say human rights organizations, is that the army's credibility suffers when it is involved in investigating itself. This is critical because as the number of civilian deaths rises, public support erodes for President Felipe Calderon's army-led offensive against traffickers.
Mexico's Senate voted last week to limit the deployment of troops and to assign civilian prosecutors to cases of military abuse. The lower house of Congress has yet to vote on the measures, and won't do so until the autumn.
In the case of the two university students killed in Monterrey on the night of March 19, the attorney general's office took the lead in a still ongoing inquiry.
In a hastily called late-night news conference on a national holiday over the weekend, prosecutors suggested the two engineering students were caught in crossfire during a running battle between army patrols and traffickers. Jorge Antonio Mercado, 23, was killed by gunshots of a caliber used by drug traffickers, while the bullets that killed Javier Francisco Arredondo, 24, were too badly damaged to determine caliber, attorney general spokesman Ricardo Najera said.
Peppered with questions from angry journalists, Najera insisted, "The case is not closed." He also confirmed that the army had tampered with the crime scene and announced the creation of "immediate response" prosecution teams to act when civilians are killed.
The students' prestigious school, Monterrey Tech, demanded a fuller report, as did relatives. Commentator Denise Maerker asked in a column: "Incompetence, or cover-up?"
"If they were killed in a crossfire, then why were they inside the university installations" as video has shown? Rosa Mercado, mother of Jorge Antonio, said in a television interview. "If they were killed by gunmen, why were they initially mistaken for gunmen?"
Calderon has insisted, accurately, that the majority of the nearly 23,000 people killed since he launched the crackdown in December of 2006 are traffickers, their hit men or security forces. But killings of civilians, including many children, have spiked significantly in the first four months of this year, outpacing all previous years.