Here’s a way to deescalate an aggressive person
Take out a pen and paper and start writing out everything they say.
By taking down notes, you're doing two things:
You're showing that you're taking this really seriously, and
You’re taking the focus of their aggressiveness away from you, and towards another object…their words.
By capturing their own words, taking the spotlight away from you, giving them another focus, you may just help them gain some perspective on their behavior.