"Sad to report that the number of fatalities increased by one," the El Paso Police Department said via Twitter. "Victim passed early this morning at the hospital."
On Saturday, a gunman opened fire in a Walmart shopping centre, killing 20 people and injuring 26. The suspect, who was identified as Patrick Crusius, surrendered to police outside the store.
Mexico's Foreign Minister Marcelo Ebrard said that his country views the El Paso shooting as an act of terror, adding that Mexico's attorney general was considering to take a legal action to extradite the shooter.