I have to agree with Walter. It also sounds like this employee may be looking for a severance package. I’d suggest someone (his immediate supervisor) pull him aside and calmly tell him that he has two choices…do his work and keep quiet, or leave. The other thought I have is that obviously there’s something going on here. If the overall feeling is that this employee is a 9-5er only, and gives nothing more than his job requirements, does he know that this is the perception of management? Has he had a performance review?
Perhaps that would be a vehicle to clear the air.