My sympathies.
Can you, please, cite the exact growth rate, that is from 5"-6" to 14" in how many months? And what temp it was kept at and what he ate and how often?
FWIW, just a reminder to OP and all that Necrocanis is always interested in dead catfishes. He dissects them, studies them, and mounts their skeletons for his scientific interests. Just place the cat in a freezer and shoot him a PM. He'll pay for shipping. More than likely too late for this cat and I would not know if 14" is big enough for Necrocanis' purposes. That's why I said "reminder".