Site failed after installation of Pressgrid

Hi I just purchased and installed the PressGrid theme on a development site that I am working on.

After I installed and clicked 'activate' the backend admin section of the site has vanished.
The front end of the website is display the following error: Fatal error: Cannot redeclare class WPBakeryVisualComposerAbstract in /home/xxx/public_html/go/wp-content/themes/PressGrid/admin/composer/composer/lib/abstract.php on line 11

I guess the issue is with Visual Composer (latest version) but I an unable to access the admin section to unacitivate the pluggin. Is there anything you can do to assist please?