Any other steps I should take?
Go inside the plugins/system/admintools/admintools directory on your site (on older versions of Admin Tools: plugins/system/admintools). You will see a file named main.php. Rename it to main-disable.php. This will turn disable the Web Application Firewall from executing and you can access your site's back-end again. After you have fixed the cause of your issue remember to rename main-disable.php back to main.php, otherwise your site will remain unprotected!