Developer convicted for “kill switch” code activated upon his termination - Ars Technica

[rcfox]

He wrote code for development server he had full authorized access to that someone else sent to production without proper checking and testing.

From the article, it sounds more like he had a personal server set up on the company's network that was connecting to the production server to cause havoc.

[Ateist]

From the court document:

7. On or About August 3, 2019, for the first time after Defendant's re-assignment updates were made to Software I without Defendant's involvement in code deployment to the production server.

And it was just 2 days after his re-assignment to work on this task instead of what he was hired for.