On our evening walk, we ran into this tiny snake. It was about 4 inches long and moved lightning fast. At the time I thought it might be a Plains Blind Snake but now that I have a closer look at the image, the head does not look right. It is black and the eyes look too big.
Update - According to Tim Cole at Austin Reptile Service, it is a baby Black Headed Snake. The non-venomous adult is about 8 inches long and feeds on worms and slugs.