How to remove all permission for a specific user of group from the server

Hi,
In our server I can a lot of staff’s who has left the company their accounts are disabled but from the server shared folders they are not removed. Each user has access to a lot of folder in different drives and it’s not possible to remove one by one. Is there any powershall or Icacls script that i can use to remove all folder permission access from the server for a specific user/group. If i can use the group that will be great”organization unit” all of our ex employess in an organization unit. Any help???