Texas is an open carry state but people don't do it. Even NRA is not recommend open carry.
Still only 5.3% of Texans have permits. Not everyone carries everyday and everywhere. So the chance of facing a concealed carrier is not high.
Even if a permit hold is there, he is not obligated to shoot back.
In Arizona congresswoman shooting case, there was a CCWer there but he was not comfortable with his skill level and chose not to act.