Again, courtesy of His Name Was Jason here are some behind the scenes photos of Doug's death in Friday The 13th Part IV: The Final Chapter. I really dig the whole behind the scenes footage from this movie. We really did not get to see any of this for any of the movies but this one. Sadly, it's all lost and gone so we will probably never unless someone other than Paramount has it.
What is so great about this behind the scenes footage is that we really get to see how these kills were done and what went into them-- that's pretty freaking awesome! In these photos you can sort of see what went into Doug's death and that his head was merely a bust prop with no animatronics/controlled eyes, just a tongue, glass eyes and blood flow.