From your description, and where you live, it sound like it "was" a Texas Brown Snake(Storeria dekayi texana).
One thing is absolutely certain, and that is that it was a totally harmless snake that you killed for no good reason. There is NO venomous snake in the U.S. that fits that description at all.
~Doug

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"a snake in the grass is a GOOD thing" 
my website -Serpentine Specialties

