Someone I knew caught a raccoon and tried to euthanize it in a freezer which I quickly put a stop to and instead opened a CO2 bottle in the freezer which quietly put an end to the issue.
Hypothermia is a "better" way to go then co2 asphyxiation if your temperature is sufficiently cold, probably hard to do for a raccoon since they can survive winter. Next time use nitrogen or helium, or like most people do, shoot it.
