As I see it, there are several things here.
On surveillance tape of the day of the incident, a man apparently slaps a woman in the face. Within seconds Haskett tackles him. Seconds after Haskett re-enters the store and then collapses. Police say he was shot multiple times.
One, based on the article, the employee seems to have over-reacted. I'm not saying he should not have intervened at all, but it seems he tackled the boyfriend and proceeds to follow the guy outside where he is shot. (my interpretation based on the article, may or maynot what happened). In my oppinion, simply speaking against the boyfriend may have sufficed; if he had escalated it, it may be another matter.
Two. I in no way see this as a work-related issue, but perhaps one of civil decency. Sure, to some extent, employees are to help maintain order within their place of work. This can be done by asking said offender to leave or calling the police. An employee has no business to attack someone for any reason (again, my interpretation) and has now become the agressor by doing so. As such, I see no reason why the company's insurance should be held liable at all.
Third. I see little application from this case to one for concealed carry holders, other than not to unlawfully attack people for a third party's benefit. Frankly, if the employee did initate the attack against the boyfriend, the boyfriend could verywell have been acting in self defense in shooting the employee.
One must always consider when and why to step in to aid another. I've been brought up on the school of thought that "evil prevails when good people do nothing" and think that a confrontation isn't out of line in this case. Assaulting the boyfriend back hardly seems appropriate, though. However, your actions are your responsibility, so you must decide on what grounds you are acting, and what you are willing to accept in doing so.