Five cannibals

Five cannibals get appointed as engineers in a defense company.

During the welcoming ceremony the boss says, "You're all part of our team now. You can earn good money here, and you can go to the cafeteria for something to eat. So please don't trouble any of the other employees".

The cannibals promised.

Four weeks later the boss returns and says, "You're all working very hard, and I'm very satisfied with all of you. However, one of our janitors has disappeared. Do any of you know what happened to him?"

The cannibals all shake their heads no.

After the boss has left, the leader of the cannibals says to the others, "Which of you idiots ate the janitor?"

A hand raises hesitantly, to which the leader of the cannibals replies, "You fool! For four weeks we've been eating Team Leaders, Supervisors and Project Managers and no one noticed anything, and you have to go and eat the janitor!"