How do you get all four death masks in resident evil 1

Each death mask is located in different areas of the mansion. The first one you get to get is where you use the Herbicide. The 2nd one is in the knight's room near Richard. You have to do the little puzzle on the jewelry box in order to get it out. Another thing is you get to figure out the order of the knights go in. The 3rd on is in the crow room near the exit of the mansion. The 4th one is located in the room where you verse Yawn. You actually don't have to hurt it at all. You can just run and get it. Take all 4 to where you used the Arrowhead. The rest is up to you.