Sounds like WalMart did nothing to ensure the safe entry of persons into the building. They seemed to have unlatched the doors and let all hell broke loose.
If they hadn't planned on such a crowd they should have got the cops to come in - before the doors opened - to address the gathered crowd and ensure some civility on entry. Even have the cops disperse the crowd and call off the sale if the crowd was not looking friendly.
If WalMart had any common sense they would have given people numbered cards in order of arrival, and once a magic number (say 250) was reached, send any other arrival home for safety reasons.
Or before the doors opened, have some security brought in to talk to the crowd, sort out a cue, put barriers in place to stagger the approach into the store etc.
Heck, any system of crowd control would have been a lot better than what seem to have happened.
The people who rushed past the injured man and those who stomped on him to get into the store, should at least be questioned by Police. A lot of them could be easily identified by security footage of who hit the guy as he was on the ground, and then whether they used a chargecard or credit card for later purchases as a means of identifying them. Even if they were only questioned, they'd soon realise they are close to being charged with manslaughter.
Crowd mentality is a real powder keg. If not properly controlled it will explode. I have had enough experience standing in front of hundreds of people to know you cannot be slack and assume they won't surge forward. You really have to engage people, give clear and direct instructions, make sure people have enough room to move a bit (and breath).
Condolences to the deceased's family. It is not expected that when you work for WalMart that you would end up dying on the job. Police, Military people, they accept that sort of risk, but not a retail shop employee. If there has been any sort of negligence or ignorance of proper safety diligence, I hope the money the deceased's family ends up winning will somehow enable them to get on with their lives after this tragedy.