Mexican Secretary of Foreign Affairs Marcelo Ebrard on Sunday announced that his country will take legal action over Saturday's mass shooting at a Walmart in El Paso, Texas.

President Andrés Manuel López Obrador has instructed officials to make sure "the position from Mexico translates first as protecting the affected families and after in effective, swift, expeditious and forceful legal actions" to protect Mexicans in the U.S., Ebrard said in a video posted to Twitter.

"What happened was inadmissible, and today at 4:30 p.m. we'll reveal the first judicial actions the government of Mexico will take in accordance with international law," he added.

The mass shooting left 20 people dead and 26 others wounded.

Patrick Wood Crusius, the alleged gunman, drove eight hours from the Dallas-Fort Worth area to El Paso, which is directly across the border from Mexico's Ciudad Juárez and is about 80 percent Hispanic, according to authorities.

"Mexico manifests their profound rejection and complete condemnation of the barbaric act where innocent Mexican men and women lost their lives," Ebrard said Sunday, not giving a number of Mexicans killed.

He added that nine Mexicans were wounded in the shooting.

Crusius allegedly wrote a racist, anti-immigrant manifesto before the attack, which described fears of a Latino "invasion."

"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 on Saturday. "NO to hate speech. NO to xenophobic discourse."