Go for the Throat

Kakashi has lost a lot in his life and it has only made him more protective of what and who he has left. So what happens when one of those people is threatened? Well, the Hatake are said to have wolf blood in their veins - Kakashi does what any predator would; he goes for the throat.
OR
Uchiha Shisui is a member of Kakashi's team (or used to be) and when he's attacked, Kakashi gets really angry. Bloodshed follows. But hey, at least he stops a massacre.