I can’t answer your question exactly but I have been in a warehouse when a tornado warning was issued and the warehouse in the path of the storm. They got everyone together and put us all against the strongest wall furthest from the approaching tornado. (It lifted before reaching us)
And you know that how precisely?
Source: my phone blew up with 3+ emergency alerts starting at around 8. (here's a NWS tweet from 7:45 -- you can see what we were dealing with: https://twitter.com/NWSStLouis/status/1469483383994691586)
Things can get out of control quicker (15-20 minutes warning is usually as close as it gets), but I think it's definitely reasonable to suspect negligence in this instance. There are two possibilities, imo:
1. They had enough time to get people to shelter, and chose not to 2. The facility wasn't up to par