"There was an occasion where a disgruntled former employee entered the building and started an altercation with our manager. They immediately responded defensively by calling security. This agitated them more, and that's when I stepped in. I asked the former employee why they felt the need to come into the office and express their grievance. I asked several follow-up questions and validated their emotions and perception of their experience. I then objectified the situation to them and help them look at how they were worsening their situation as we spoke. I was able to illustrate that the behavior they'd been displaying resulted in them being let go in the first place. After rationalizing with them for a while, I was able to de-escalate the situation, and they left peacefully, apologizing to everyone involved."
