I doubt I would lay down and play dead, I might chose to hide or fight back depending on the situation. As was mentioned there's always something near by that can be used as an improvised weapon.

Thats something else I have always been thinking about, how to handle the responsibility of the business owner, I mean should they be required by law to have armed guards at all entrances and exits to prevent such things, they would have to be armed and trained because an unarmed guard would just be another target.