As bad as it is, it's also a good situation to learn from. What would you do if you were in that Walmart (By yourself, with your family)?
It really depends on where I am in relation to the mob when it begins.
1. Get as far away from the mob as possible.
a. If at ground zero when it begins, do whatever it takes to get away/out.
b. Leave store if it doesn't require pushing counter to the mob (i.e., go out the other exit if possible).
There's too much risk going into the mob for any reason, in my opinion.
c. If unable to confidently leave store, move to other corner of store.
2. Avoid confrontation
a. Don't appear to be an easy victim.
b. Don't appear to be a threat.
c. Give them no obvious reason to come after you.
3. Find a corner with good sight lines that's easily defendable. A corner limits exits, but also limits entrances.
4. Limit who is allowed in your secured space (Not immediately threatening).
a. Obviously or questionably with the mob, they don't come near.
b. Obviously not with the mob, case by case situation depending on their needs, attitude, and ability to aid in defense.
5. Deal with obvious threats accordingly.
6. Make a quick exit when a safe opportunity arises.
7. Hope 10+1 with a spare 15 rounds of 9mm is enough.
For the record, I'm single with no kids. I think my plan would be applicable with a family though. I hope that my future wife would be armed as well and could aid in defense.