Can your staffs distibute your company non-distirbuted GPL licesned code?

Let say you use libmysqlclient to connect to MySQL, and since the client is GPL licensed and so your program. That's fine since you are the only one working on the project.

Then, you have a staff to join and contribute to the program, and he left. He own a copy of the program, can he freely distribute it because it is GPL lichened?