1. The company should be able to fire whomever they want to fire for whatever reason they deem necessary.
2. The company, like most large companies, had a policy that stated that employees should not intervene in robbery attempts; the company, most likely, had insurance to back up the theft. That insurance deductible is most likely lower than would have been the deductible had the man been seriously wounded.
3. The burglars were trying to steal money from the company not from the employee.
4. The burglars, according to the article, did not verbalise their threat until the employee refused to give them money.
I worked retail in high school (Old Navy) and was subjected to a video on the first day of work in which I was admonished not to try to intervene in any robbery but simply inform my supervisor and/or call the police.
Whether or not one agrees, philosophically, with this stance is certainly debatable; however, these companies have these policies in place in order to avoid the potentially larger and more devastating costs of lawsuits that could/would occur in the event that something went horribly wrong in the intervention.