Putting it in the freezer put the fish down in less than a minute.
No it doesn't. There's been instances where fish appear dead or "asleep" after a few minutes in the freezer and start responding again after being put back in warm water... or flushed, where they suffer a horrible death swimming in sewage. The correct way is to leave the water in the freezer until it's almost frozen, then pull the fish from the warm tank and drop it in the ice water, the sudden drop in temperature will kill it instantly.