The 21-year-old Patrick Crusius admitted to investigators that he carried out the shooting at a Walmart shopping centre in El Paso and was intent on targeting Mexicans, an arrest warrant affidavit obtained by the Washington Post revealed.
Following the mass shootings, US President Donald Trump said in a statement that "serious discussions" are taking place between congressional leaders on implementing meaningful background checks for individuals purchasing firearms in the United States.
He expressed the confidence that lawmakers will get a "very good package" of gun control measures.
At least 22 people were killed and more than 20 wounded after a gunman opened fire in a Walmart shopping centre in El Paso, Texas, on Saturday evening. Less than 24 hours later, a gunman killed nine people and wounded 27 others in a separate shooting in Dayton, Ohio.