We heard it, too. My husband made me mute the TV, asking "What is THAT?" It was a rumble that lasted about 15 seconds and he decided it was a train, but I don't recall ever hearing that before. Gives me chills.
God be with their families.
I live in south Louisiana, app. 300 miles from Dallas, and that's exactly what I heard too. Hard to describe what it sounded like, but it was definitely loud.