...and I would guess that he used the knife in a stabbing brather than slashing manner in order to inflict fatal wounds.
And I would guess he wasn’t thinking strategically, just reacting automatically. I seriously doubt he was thinking through the implications of each thrust of the knife. My bet is he was thinking...
“Being attacked. Must defend. Being attacked. Must defend. Being attacked. Must defend.”
I highly doubt his thought process went beyond that. I have no clue if he has martial knife training. If so, then he fell back on his training. If not, then the above is all he could handle.