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Mexican officials on Sunday angrily denounced the mass shooting in El Paso and announced a series of unusual actions to protect Mexicans in the United States - including possibly charging the perpetrator in Mexican courts.
Foreign Minister Marcelo Ebrard said the country would take action under international law.
"Mexico declares its profound rejection and complete condemnation of this barbaric act, in which innocent Mexican men and women lost their lives," Ebrard said in a recorded message on his Twitter feed.
The remarks represented a toughening of Mexico's official reaction to the shootings. On Saturday, López Obrador appeared to play down any US government responsibility for the violence, saying the attack was "a product of [societal] discomposition, of problems certain people have. It's not a generalised issue."
El Paso mass shooting: 20 killed at Walmart store
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But there were increasing indications that the shooting was aimed at Mexicans. Investigators are studying a manifesto that they believe the suspect posted online before the attack; it includes screeds against immigrants.
"The intentionality of the attack against the Mexicans and the Latino community in El Paso is frightening," Mexico's ambassador to Washington, Martha Bárcena, wrote on Twitter. "NO to hate speech. NO to xenophobic discourse."
He has consistently highlighted his good relations with Trump.
Analysts believe López Obrador has been anxious to avoid antagonising Mexico's largest trading partner, the recipient of 80 percent of its exports.
But there was no missing the officials' angry tones on Sunday.
"Mexico is indignant," Ebrard told journalists. "But we are not proposing to meet hate with hate. We will act with reason and within the law, but with firmness."
He said Mexico would ask US officials how the gunman obtained his weapon. The Mexican government would also ask Mexico's attorney general to consider charging the suspect, identified as a 21-year-old Texan, with committing terrorist acts against Mexicans in the United States.
"As far as I know, this would be the first case of this type in history," Ebrard said. The Mexican government could even seek to extradite the suspect, he said.
"For Mexico, this individual is a terrorist," he said.
Ebrard said Mexico would send a diplomatic note to Washington "asking respectfully but firmly that they take a clear, strong position against hate crimes."
Mexico is planning to convene a conference with other Spanish-speaking countries that have immigrant communities in the United States to promote their defence, Ebrard said.
He identified six of the Mexican El Paso victims as Sara Esther Regalado of Ciudad Juarez; Adolfo Cerros Hernández of Aguascalientes; Jorge Calvillo García of Torreon; Elsa Mendoza of Yepomera; Gloria Irma Márquez of Ciudad Juarez; and María Eugenia Legarretta Rothe of Chihuahua City.
Mexican media identified Mendoza as the principal of the Rafael Veloz primary school in Ciudad Juarez, just across the border from El Paso. The newspaper Reforma said she was killed while in the supermarket section of Walmart in the Texas city.
López Obrador is a longtime defender of Mexican immigrants in the United States. In 2017, a year before his election, he published a book of his speeches and proposals to support Mexican migrants called "Listen Up, Trump."
Shock at the shooting rampage reverberated through Ciudad Juarez. Many residents routinely cross the border to shop or visit family and friends in Texas.
On Sunday, as on most days, there were long lines of cars waiting to head into the United States.
But some drivers told Mexican reporters that they were nervous about their safety on the US side - an ironic sentiment, given that, unlike El Paso, Juarez is violent, with more than 800 homicides recorded from January to mid-July.
The Washington Post
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