I'm pretty sure walk-in ovens, like walk-in freezers, are supposed to have a few safety features like interior handles that open regardless of any outside lock, alarms, etc.
This is certainly suspicious af.

The management might have preferred the store closure to having the bakery department marked off with crime scene tape in full view of any customers. And the cops probably appreciated not having a bunch of lookie-loos staring at them across the tape. Plus I imagine that the dead woman's mother isn't the only employee dealing with shock/mental health issues because of this. They may not have been able to get enough staff willing to come in to reopen the store immediately.

(TL;DR: There may well be something ugly going on here, but I don't think the store being closed is enough evidence to prove that on its own.)

Regardless of foul play, this is awful and deserves a thorough investigation.

Either the security protections weren’t good enough, protocols weren’t followed, or something else happened that needs to be understood (accidental or otherwise).