You can't possibly prepare for every situation. However, you can (and should) prepare for generic situations so you and your team can know how to act. This is connected to the magic portal idea that once you start working, the rest of the world doesn't magically disappear from your mind. The corollary of the magic portal idea is that outside events will impact inside the workplace, be prepared for them.
There are some events that impact everyone, for example, the 9/11 attacks or the recent violence in the Capitol regarding the election. These are major events and can't simply be ignored. You should have a plan in mind for how to handle these events. The difficult part is that these events will all be different and have different levels of impact. In addition, your team will be unique in how it feels and handles these situations.
The fact that we dealt with one of these situations recently is a good time to take some time and reflect. How did you handle it? What did you do well and what could you do better? How did your team react? Maybe even talk with a few team members individually and ask how they dealt with it. You may think they weren't hearing or thinking about it, but only because you didn't see them doing it. If you have a good relationship, they will be honest with you.
Here are just a few of the questions you may want to ask yourself:
When the incident happened, what did I feel and do?
How did my team react? Was anyone distracted or upset?
Did I address it with the team? Could I have done better addressing it?
Did the incident impact productivity?
As you start to think about these questions, more will come to mnd and you should consider them all. The goal is to create an idea in your head about how to behave when these types of incidents occur. You have to start thinking about these things in advance because when they happen, it will be too late.
Two last quick thoughts:
Those who say "those instances are so rare that it is a waste of time to think about them" are wrong. How many times has a tornado or earthquake caused damage to your company's office? Yet they still have a plan.
I am referring to events that are public and the impact is huge. If it becomes an individual issue, obviously those need to be handled differently. However, don't discount the impact to the team. If the spouse of a team member dies unexpectedly, it obviously impacts that team member, but the rest of the team may grieve in different ways themselves.