The attacks came less than a week after a 19-year-old gunman killed three people and injured 13 others at the popular Gilroy Garlic Festival in California before dying of a self-inflicted gunshot wound.
The former president also calls on law enforcement and internet platforms to find ways to "reduce the influence" of hate groups, pointing to the fact that the El Paso shooter appears to have been "radicalized by white nationalist websites".
The U.S. Attorney's Office for the Western District of Texas John F. Bash said, "We are treating this as domestic terrorism".
O'Rourke went on to say that he stands by his city and he is so proud of the way the community has come together after Saturday's incident.
The U.S. Border Patrol has re-opened its inland checkpoints around El Paso, Texas, after closing them for several months due to staffing shortages.
The Texas rampage was followed just 13 hours later by the mass shooting in OH and came a week after a man shot dead three people at a California garlic festival before taking his own life.
A four-page statement posted on 8chan, an online message board often used by extremists, and believed to have been written by the suspect, called the Walmart attack "a response to the Hispanic invasion of Texas". The agency closed them in March because agents were needed to process and detain surging numbers of migrant parents and children.
He said he could only speak of the female victim who died.
The Del Sol Medical Center did not release the names or ages of the patients who died, but hospital officials described one as an elderly woman. An El Paso hospital announced another death later increasing it to 22. Though the two attacks staggered a nation accustomed to gun violence, the bigger shock may have been that the death toll wasn't worse. Roughly two dozen other people were wounded.
He was quickly killed by police.
While criticising the facility with which firearms can be obtained in the U.S., the La Jornada editorial said the motivations behind the El Paso shooting appeared to be, "as in previous cases, openly racist and anti-immigrant, in consonance with the discourse of President Donald Trump, whose sinister resonances support (although he officially condemns the events) all the stupidity and barbarism that are shown by massacres such as that of yesterday [3 August]". He had previously said there were seven wounded, but that figure was not updated.
Patrick Crusius, 21, has been charged with a single count of capital murder in the El Paso case, court documents show, in what is likely a legal place holder to keep him in custody while the investigation is under way.
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Police said Sunday that all bodies have been removed from the store and its parking lot, and that the attack did not spread to other nearby shopping areas.
El Paso Police Chief Greg Allen said the suspect was cooperating with investigators.
Allen is more than 600 miles (965 kilometers) from where Saturday's rampage occurred.