That being said, if you are ever face to face with "holy crap where did all this blood come from", you can:
A: apply pressure (with gloves on!) and every bandage in your first aid kit, or
B: apply pressure (with gloves on!) and a couple of these:
QuikClot is used to stop bleeding from gunshot wounds, and is good for that and most other wounds that involve a lot of blood loss. I carried a pack on my person, and so did some other cops I knew. Don't ask me how it does what it does, it just works.
You should still apply pressure, and a dressing over the wound. The sponges are less messy and easier for the doctors to deal with than the granules, so open the package but not the sponge inside. The sponge shows up on xrays, but you should still pin the empty package OF EVERY SPONGE YOU USE on the clothing of the person who you use it on so they can fish them out at the hospital. Oh, and they get hot when applied, so don't freak out. That means they're working, and however badly it hurts won't be as bad as bleeding to death.