That's not too amazing -- Texas has a population of 21.3 million, on 267,000 square miles. That's 349,000 square feet per person. If we estimate that a person occupies a surface rectangle of about 2x3 square feet, means that any given square foot of Texas has a 58,243 to 1 chance of being empty of people. So a given chunk of incoming debris has around a 99.9982% chance of missing everyone in Texas when it lands, and hitting unoccupied space.
Even if the shuttle came apart into 10,000 individual pieces, indicating an average piece weight of 18 pounds (and I'd think it would be fewer pieces), that works out to an 84.2% chance of every single one of them missing folks as they land.
And those are the odds presuming that everyone in Texas is outdoors and vulnerable to being hit -- realistically, most people would have been indoors or in cars, or otherwise shielded from incoming pieces, so the odds would be even greater of no one at all being dinged.
Saturday morning in Texas means that a lot of people are still sleeping off Friday night.
God bless the families of the astronauts. May they gain closure from interring the remains of their loved ones.
/john