Unable to remove .ics imported calendar events

I have an employee who downloaded and opened a .ics file, which populated her groupwise calendar with events. When trying to delete them, they will not go away. No sub-calendars have showed up in the side folder pane. When going to manage calendars, only the main calendar shows up. Is there a way to remove all of the events? She has resorted to clearing the data from the events one at a time, so they do not clutter up the calendar, but I was assume there is a way to completely remove them. Any help is appreciated. Any additional info needed, please ask.

Thank You.