Complex sentence: Austin patrolman Billy Speed was one of the first police officers to arrive at the University; he and a colleague took refuge behind a columned stone wall, through which Whitman shot through the six-inch spacing between the columns of the wall and killed Speed.
Split into simpler sentences: Austin patrolman Billy Speed was one of the first police officers to arrive at the University. He and a colleague took refuge behind a columned stone wall but Whitman shot through a space and killed Speed.