Crawfish is dieing how can i put him out of his misery?

My little bro isn't doing good and i can tell he is on his death bed... at the moment the most painless way i have found is to put him in a freezer an then why they ae sleeping stab them but i really dont want to stab my bro and I have also heard they can survive the could so any ideas? at the moment i have in the freezer so he will slip into unconsciousness so it will stop his suffering....