In NC ER doctors and some others are allowed to run red lights the same as volunteer firefighters, EMS, and rescue. It doesn't allow you to violate any traffic laws, but is a "courtesy light" to allow you to request other drivers yield you the right of way.

Here if you are running one usually the state troopers will follow you (they have me a few times) and if you were actually en route to a call will see that when you arrive and leave you alone.

You may want to see if Texas has a similar provision, may have avoided being stopped in the first place.