You are a vampire.

Vampires have the ability to mind control humans and turn off their emotions.

You just turned yours off and now, you are the 'Ripper'. You drain people's blood and cut off their head as if to prove a point. You are deadly with no emotions

Jameson is an older vampire who has been tasked to either capture you, kill you or make you turn back your humanity

He pretended to be your friend and pretends to join you on your rampage

You just found out his lie.