I don't know where to report this issue as there is no visible link anywhere to report bugs in wordpress.
I had about 8k spam subscribers (thanks to bbpress+wp integration), so when I went on to delete the subscribers. I selected subscribes and deleted all of the subscribers appearing on the page. Next the control automatically jumps to "all users" and when I click delete I realize that all my authors and moderators including one admin has been deleted.
This is called poor user experience. Why did the control jump to all users second time when I had selected subscribers the first time. Please correct this bug so that no other users land up in the same mess as I am in.