A gunman killed at least 20 people and wounded 26 others at a Walmart shopping center in El Paso, Texas on Saturday, before being arrested in the latest mass shooting in the United States. El Paso police have ruled out multiple shooters, and initial reports showed that the gunman used a rifle. The suspect, now in custody, was identified as a white male in his 20s. The rampage took place as shoppers were buying back-to-school supplies.