I think one of the best sources about how people actually behave in disaster situations is still Amanda Ripley's 2009 book "The Unthinkable: Who Survives When Disaster Strikes - and Why".

A few panic, a few are clear headed and do well, but most just wait passively for someone to tell them what to do. Since taking bags is what one normally does when getting of a plane, they will take bags (unless someone orders them not to).

One of the best things someone could have done in that situation would be to have yelled as loudly and forcefully and aggressively as possible "YOU! ...LEAVE THE BAGS! ....GET OUT NOW!"