UN Secretary-General Antonio Guterres condemned "in the strongest terms" Monday a mass shooting in El Paso, Texas, his spokesman labeled a "terrorist attack."

Axar.az reports citing foreign media.

Stephane Dujarric said Guterres further "expresses his shock and outrage over the mass shooting only hours later in Dayton, Ohio."

Guterres "extends his heartfelt condolences to the families and loved ones of the victims and expresses his solidarity with the peoples and Governments of the United States and Mexico, from where a number of those killed and injured in the El Paso attack hailed," Dujarric said.

"The Secretary-General stresses the need for all to work together to counter violence rooted in hatred, racism, xenophobia and all forms of discrimination," he added.

Federal prosecutors are handling the mass shooting in El Paso as a case of domestic terrorism.

The suspect, 21-year-old Patrick Crusius, was taken into custody after 20 people were killed and 26 others were injured. Two of the injured died in a hospital Monday, raising the death toll to 22.

Just minutes before the tragedy a racist essay was posted to the website, 8chan, titled, “The Inconvenient Truth,” which railed against an alleged "Hispanic invasion of Texas,” and assailed "race-mixing" while pledging an imminent attack.

“I am simply defending my country from cultural and ethnic replacement brought on by an invasion,” it said. "This is just the beginning of the fight for America and Europe. I am honored to head the fight to reclaim my country from destruction."

The Walmart shopping complex is located just minutes from the U.S.-Mexico border, and many of the victims were Latino, including seven Mexican nationals.

El Paso Police Chief Greg Allen said investigators are attributing the writing to Crusius who is a resident of Dallas.

About 13 hours after the tragedy unfolded another rocked Dayton, Ohio, when a body armor-clad gunman opened fire in a popular nightlife area.

He was quickly killed by police. But in the 30 or so seconds that passed after the individual identified by police as Connor Betts, 24, opened fire, nine people were killed and over two dozen others were injured. Among the deceased was Betts' sister, Megan Betts, 22.

The motive in that shooting remains unclear.