We had our work Xmas meal last night.
I manage a team of around 20 people, my managers were also there. One member of staff I’ve had repeated issues with over the last year (turning up late, gossiping, not pulling their weight)
Towards the end of the evening I was having a conversation with some people on our table about some of the food options (the food was a disaster but it had become a kind of running joke of the night). We were all laughing and joking. Member of staff I’ve had issues with turned around from another table and very loudly shouted
“Oh will you shut the fuck up” at me 

My table had my managers on it. Two of who looked at me like WTF. I just looked at member of staff and raised my eyebrows.
What would you do about this?