Group Owners can delete any Events they have created within their Boomset Groups and Subgroups.
To delete an Event, navigate to your group and look for the Events' page. Next to the event you want to delete, you should see a trash icon under the Actions column: 
Click on the icon to start the deletion process. After doing so, you will be prompted to enter your password to complete and save the action.
Note: If you choose to delete an event, this will erase the entire event and all of its data. Proceed with caution as the data cannot be retrieved once deleted.