In general, an account for an employee that has ‘moved away’ (for any number of reasons) should have their access privileges immediately downgraded. I would also change their password to prevent access.
There are many instances of a former employee still having access, and doing improper things to the business computer systems.
When an employee leaves (or is ‘asked’ to leave), their access to anything should be severely restricted, even if they are given a two-week transition before actually leaving. This is especially true for the employee that has administrative access to anything in the company computer systems.