Further reason why I think the proper response to the Mexican authorities

would be "Kiss our ass, you socialist bastards."
Shortly after the boy was shot, Mexican soldiers arrived at the scene and pointed their guns at the Border Patrol agents across the riverbank while bystanders screamed insults and hurled rocks and firecrackers, FBI spokeswoman Andrea Simmons said. She said the agents were forced to withdraw.

"It pretty quickly got very intense over on the Mexican side," she said, adding that FBI agents showed up later and resumed the investigation, even as Mexican authorities pointed guns at them from across the river.
Here's a part I call bullshit on:
A relative of the dead boy who had been playing with him told the AP that the Mexicans — who he described as federal police, not soldiers — pointed their guns only when the Americans waded into the mud in an apparent attempt to cross into Mexico.
Does ANYBODY actually believe a Border Patrol agent, in front of lots of witnesses and Mexican authorities, would try to cross? Bullshit.
Hernandez was found 20 feet (six meters) into Mexico, and an autopsy revealed that the fatal shot was fired at a relatively close range, according to Arturo Sandoval, a spokesman for the Chihuahua state attorney general's office. Mexican authorities said a .40 caliber shell casing was found near the body, suggesting that the Border Patrol agent might have crossed into Mexico to shoot the boy.

That would violate the rules for Border Patrol agents, who are supposed to stay on the U.S. side — and could open the agent to a Mexican homicide prosecution.

A U.S. official close to the investigation told the AP that authorities have a video showing that the Border Patrol agent did not cross into Mexico. In fact, the official said, the video shows what appear to be members of Mexican law enforcement crossing onto the U.S. side, picking something up and returning to Mexico. The official was not cleared to speak about the video and spoke only on condition of anonymity.(Hey, they needed evidence to plant, give 'em a break!)

Alejandro Pariente, Chihuahua state's regional deputy attorney general, said the U.S. Border Patrol has given him video which he is reviewing. He declined to describe it except to say that it has sped up the investigation.
"I can't comment because the video says our account is a pile of diseased donkey droppings."

And of COURSE it's the fault of Arizona:
"We believe that this killing, the second in recent days in the border between the two countries, is due to xenophobia and racism, derived from the approval of Arizona's anti-immigration law," Reyes said.
Oh, of COURSE it is; couldn't POSSIBLY be because a bunch of thugs were stoning the agents, now could it?

Screw Mexico. They're so damn worried about this? Seal the border, then they won't have to worry about illegal border crossings, will they?