When you have to fire somebody from a company, the standard legal recommendation is that managers shouldn’t talk about the situation at all, because doing so risks defamation.
That is, you might say something about the employee that they could then sue the company over. That’s reasonable advice most companies want to follow, plus managers often don’t want to spill details out of respect for the person they’ve let go or for people who were affected by the person’s actions. But silence is also at odds with the sort of internal transparency that many organizations – especially small or young teams – frequently strive for.