Needs a bigger gun!
First and foremost, every employee that works there should be required to carry the largest caliber firearm they can competently and safely handle.
Second, they need to be educated on the law in regards to firearms and using them at their place of work and other places.
Third, they need plenty of range time and tactics training. They also need to be willing to actually use their firearms against another person when it comes down to brass tacks.
If they had above three, at least one or two would not have made it out the door. A couple more might have bled out on the way to their getaway vehicle.
AND, he needs more range time!
He should have been able to shoot one or two more!
FATALLY!