Reading your comment I realized that you are more than I connecting together the decision making part of firing someone and actual action to be made.
I was taking about red flags. Like stealing something which is found on cameras, like making a fight etc.
But I also meant such signs as: person is not able to fulfill the task in a week and you see all the signs that it wont start improving, or say someone is late to the office starting the first day and the overall communications show you that this wont improve.
I am talking about signs that you as a manager find and make the final decision and does not matter if it took you a week or a minute.
Working with people and letting them know upfront that something is wrong is a separate thing. I am strong believer that sometimes it is just waste of time.
That's execution without judgment, even a simple hearing might not be enough because the circumstance might be complex
But dont you remember stories from your life when you met people that telling from all your experience would not improve on performance? Or say you dont have time to teach anyone life or work ethics?
Managers are here to save everyone time I guess. Firing very often is saving everyone time.
Bottom line can I fire someone simply if I dont like them? Thats a question for the next Ask HN)))
Immediate firing should be reserved for severe situations like breaking a law while at work, fraud, sexual harassment, physical violence etc.
For anything else like performance and personality issues, you should have a systematic way of giving feedback and working through these problems so that if you ever fire anyone, it doesn't come as a surprise to them. And if you ever fire anyone for something like low performance and this is surprising to them, you as a manager haven't done your job well.