Wrong content being deleted - Deleting 2700 users

I have around 2700 users to delete (import of users failed). I show only rows with a given role, I select all 50 rows, click to select all 2700 rows, drop down and select delete, verify that the first 50 are users, confirm. It deletes content, then I am shown the users page with some users still in that role and certain non-user nodes are now deleted.