When Richard Alpert visited a young John Locke at his foster home, he saw Locke's drawing on a wall. The drawing showed a prostrate stick figure with an unhappy expression on his face. A scribbled mass covered much of the page, including some of the figure.
Richard showed some interest in the drawing and asked whether John had drawn it. Already believing in a connection between Locke and the Island, Richard likely interpreted the drawing as a depicting the Man in Black attacking in his monster form.