A grainy mobile phone video has cast doubt on a US border patrol agent's claim that he shot dead a 14-year-old Mexican boy after he was threatened by a group of illegal immigrants.
The footage captures the moments before Sergio Adrián Hernández Güereca was shot in the head on the concrete banks of the Rio Bravo, which at that point is a 10-metre stretch of mud dividing Ciudad Juarez from the Texan city of El Paso.
The killing by US authorities — the second in less than two weeks — has enraged Mexican opinion and exposed the deep distrust between the two countries, with officials from each government making veiled accusations of misconduct by the other's law enforcement agents.
US authorities say the agent was acting in self-defence as he sought to repel a group of would-be migrants hurling rocks. The boy's family claim Hernández was innocently playing with friends. Neither version of the events has been confirmed by multiple eyewitness accounts reported on each side of the border.
The video, taken from a nearby pedestrian bridge shows three people running from the US bank of the river, towards Mexico, chased by border patrol agents. One of them is caught by an agent who drags him along the ground, keeping one arm outstretched towards Mexico with what looks like a gun in his hand.
The sound of shots follows and a voice is heard shouting: "He's hit him, the idiot, he's hit him." Another voice adds: "It's because they are throwing stones."
The video contradicts an account by FBI spokeswoman Andrea Simmons who previously said: "This agent, who had the second subject detained on the ground, gave verbal commands to the remaining subjects to stop and retreat. However, the subjects surrounded the agent and continued to throw rocks at him. The agent then fired his service weapon several times, striking one subject who later died."
Simmons also told the Associated Press that Mexican soldiers arrived at the scene soon after the shooting and pointed their guns at the border patrol agents while bystanders shouted insults and threw rocks and firecrackers their way, forcing them to withdraw. The Mexican army denied they had been present at the scene, but the federal police confirmed they had "secured" the area after the incident.
A spokesman for the state prosecutor's office, Arturo Sandoval, told reporters that the boy died six metres inside Mexico and that the fatal shot was fired from relatively close range. This has boosted charges from Hernández's family that agent may have crossed into Mexican territory to shoot the boy, and that others tried to cross later to recover evidence.
Beyond the events themselves, the character of the victim has also become a point of conflict. US officials told the El Paso Times that Hernández was on the El Paso juvenile smugglers most-wanted list. But his relatives have showed Mexican reporters school certificates they say prove he was a hard-working student. The family has also announced it will be filing charges in the US courts in search of a murder conviction.
Today, another Mexican killed by border patrol agents was buried in San Diego. Anastasio Hernández, 42, died on 28 May after he was shocked with a stun gun at the San Ysidro border crossing that separates San Diego and Tijuana.
The furore has prompted opposition party leaders in Mexico to accuse the government of being unacceptably timid in its response to the shooting, which has been limited to a couple of statements bemoaning the "disproportionate use of force" and calling on the US authorities to investigate.