A close family member died in jail recently. what could’ve happened?

She had a history of drug abuse-meth, painkillers, alcohol, etc. We’ve been told she had a seizure and died quickly, but with absolutely no forewarning. She was feeling fine, had a seizure, and died immediately. So far, autopsy shows possible alcohol withdrawal. She’d been in jail for 36 hours. What could’ve happened? Would alcohol withdrawal really kill someone that fast without showing any symptoms?