I'm just gonna like, break down the number of ways this could go wrong for us.
1) The SK is like, totally lying about what achieving their kill quota does and becomes like, a more powerful threat after Karu dies, meaning we potentially have to like, hunt for one other bad guy in addition to a rogue neutral.
2) The SK (can I just like, call him Hiram? I know that's who he is) lied and like totally kills another townsperson which means we have to like, decide between wasting the day lynching him while letting Karu like, sit for another day or let him totally get another kill that you won't be able to control.
3) Sorian and Hiram are like, in cahoots and both depart after Hiram fulfills his kill quota, leaving the rest of us like, hanging in the lurch while losing someone who despite being like, hardnosed and stubborn moves the conversation along.
4) Hiram is roleblocked by a bad guy and we kill him without like, gaining anything at all or at the very least, like, have to waste tomorrow lynching Karu.
5) Hiram is working with the bad guys and like, knows he can win if like, any of the above scenarios come to pass.
So please Mike, like, don't wait for Sorian's permission and like, pull the trigger on Karu.
It's the absolute smartest move you can pull.