How long can a Bull shark survive without any blood in the brain aka hypoxia?

I saw a video of a person who caught what appears to be a small bullshark, and he was demonstrating how its jaws can still snap shut after death, this shark had been fully gutted and drained of all blood, Im knowledgeable in the mammalian brain but not those of marine life, I ask because I would assume 5 minutes at most before the brain shuts down meaning those jaws are a post mortem response, but I looked in the comments and anyone saying its dead are just getting absolutely torn apart by angry commentators crying out "Animal abuse" and saying "Educate yourself in biology" so I was genuinely interested to know if a bull shark or a similar species could survive above 5 minutes.