What did the children see that they "ought not to have see"?

From the text:

Some more women followed, clicking their tongues and exclaiming; evidently there was something that the children ought not to have seen. I rounded the hut and saw a man's dead body sprawling in the mud. He was an Indian, a black Dravidian coolie, almost naked, and he could not have been dead many minutes. The people said that the elephant had come suddenly upon him round the corner of the hut, caught him with its trunk, put its foot on his back and ground him into the earth.