Firing someone for taking three days off to handle a family emergency is not reasonable. Your opinion of whether the emergency was caused by risky behavior is irrelevant.
I'm frankly disgusted that anyone would look at this from a purely profit driven viewpoint, especially as this viewpoint is short-sighted and mistaken.
Treat your employees well and they will usually treat you well.
There is no benefit to running your business this way. It's only harmful.