With that area being one of the thickest parts of the skull, who knows how it got in there. He may have passed out on the floor, and the the knife could have been driven in with the use of a hammer. Also the amount of blood loss, appears the the knife could have gone completely through penetrating and cutting a lot of the facial vessels, resulting in the sizable blood pattern. When I was a Homicide Investigator, I saw many fatal, cranial knife wounds. and most were almost a blood free crime scene, because if the knife was left in place, it served as a plug, and there was very little blood flow from around the blade. This is also the reason that doctors always say, if someone has been stabbed, don't pull the blade out, secure it in-place and get to ER, STAT... This is due to the risk of uncontrolled bleeding if the blade is removed, in something less that a level 1 trauma/shock room or ER.
Just some food for thought about it from a retired LEO.
Cabriolet.
Thanks! You just saved me alot of work!