Plumber capped 1/2 gas line, house filled with gas smell, he says it’s the excess gas in the line escaping.

Called our regular plumber to cap a 1/2” gas line. His brother showed up who is a “part of the business.”

He had a 1/2” black iron cap with blue sealant. He cut the attic line with a sawzall and the house filled with a gas smell. It took him a minute to twist the excess pipe off and plug the line.

He said the gas smell should fade in an hour. Said It was the excess gas in the line. We opened all the windows.

It seems like the smell is slowly fading, but is this the normal procedure?

EDIT: yes, I think he did it “live.” I showed him where the meter was and then had to step out. In hindsight, I don’t think he actually shut the gas off.

EDIT2: it’s possible he quickly twisted off the 1/2 inch line, cut the threads, and put in the plug. I heard sawing but it may have been because he just cut apart the leftover pipe. I have no idea.

For those saying “no way he did it live”, at no point did he go outside toward the gas meter. I would have heard the back door chime. So yeah…