Anna's ex Peter turned up drunk at her wedding

[Bassim]

I am wondering if my sentences sound natural. Do I need a comma after "ex" in the first sentence?

Anna's ex Peter turned up drunk at her weeding, insulting the guests. When someone tried to reason with him, Peter knocked him down. Soon the chaos broke out when the ex drew a pistol and shot in the air.

 

[teechar]

I think you meant "wedding". Also, use "chaos" instead of "the chaos" and "Peter" instead of "the ex".
I would set off the first "Peter" with two commas.

 

[jutfrank]

weeding?
just chaos not the chaos
shot into the air

No, I don't think a comma is needed.

 

[Bassim]

Here is my second try after your corrections. I will use commas as teechar says, although I have seen that some writers do not use a comma at all in similar sentences.

Anna's ex, Peter, turned up drunk at her wedding, insulting the guests. When someone tried to reason with him, Peter knocked him down. Soon chaos broke out when Peter drew a pistol and shot into the air.

 

[teechar]

Perhaps also change "people" to "the guests".