Recently, one of our managers "blew up" on another employee (not one of their directs). This manager vented a lot of anger, used foul language and hung up the phone. I have given the manager feedback and told them they need to apologize. They have agreed to apologize and want to begin to repair the relationship. The other employee was really shaken up and has refused to accept any calls or to listen to an apology from the manager. It has now been a week. At this point, the manager is very frustrated that they can't work to resolve this and is also frustrated because they need to collaborate with this employee to succeed in their job. To compound matters, the employee has told people in the organization that they have "written their letter of resignation".
Thank you in advance for any assistance,