At noon on Aug. 1, 1966, Allen Crum, the floor manager at the University Co-Op, looked out the window and witnessed several students dragging a limp teenager through the grass on the edge of the University of Texas campus.

The burly 40 year old Air Force veteran, a retired tail gunner, walked across Guadalupe Street to break up what he believed to be a fight. But as he drew closer to the circle of youths, he could see that the boy in the center was bleeding badly.

It was then that Crum heard the g...