You have to understand the psychopathic nature of a corporation to understand the firing.
Corporations exist solely to maximize profit. There is no other reason for their existence. If you as an employee are killed by a robber than there is zero cost liability by the Corporation: the medical costs of emergency services accrues to the family, the burial costs are on the family, and prosecution of the guilty is funded by the community.
I have read of Corporate “dead peasant policies” wherein they have life insurance policies on employees, but the benefits go to the Corporation, not the family. You can understand what a perverse incentive this is, to make profit on employee deaths, but that is our system.
Now if an employee merely causes a paper cut on a robber, the Corporation is liable. If an employee gets in a shoot out and one of those bullets hits a car, a customer, another employee, we are talking big liability to the Corporation.
It is good business economics that dead employees are less of a liability than dead robbers.
It may be amoral, but hey, Corporations are psychopaths, they don’t have any morals.