He described it as one of the deadliest days in the state’s history.
The massacre happened at a Walmart store last night near the Cielo Vista Mall, a few miles from the US-Mexico border.
A 21-year-old man is in custody and is believed to be the sole gunman.
Abbott praised the police officers who apprehended him.
The suspect has been named by the US media as Patrick Crusius, a resident of the Dallas area.