ok, this is how he PROBABLY made that sig. First, he found or vectored a picture (the dude blowing his head out.) When you vector, you simply take the pen tool around parts of the picture, and fill them in. in his case, he did black, white, and grey. Then, he made a new layer, brushed those black things on the top. finally, he made a new layer above all where he brushed in red. So to answer your question, he didnt make the dude black and white in the sig, it started that way.