no longer with us

Usually implies that someone is deceased, but may mean that the person is no longer associated with an organization. Potentially, the term could start a rumor that the individual is dead.

Customer: "Does Matt still work here?"

Worker: "No, I'm afraid he's no longer with us."

Customer: "I'm so sorry to hear that."

Worker: (optional) "He decided to quit last week, so he could go back to school."