A park employee told WBKO that there were no trapped riders.
Apparently a rider's seat belt wouldn't unlatch on a ride a Beech Bend and the rider's mother called 911. Fire department responded to find that -- no one was trapped because the issue was already resolved.
Shouldn't have been a 911 call, but the fire department does respond to this kind of thing because they have the equipment and training. Depending on what kind of restraint it is you might need heavy equipment to remove it if it's jammed. If it was just a seatbelt though that should be well within the park staff capabilities.
It should be the park that calls 911 if it's required though. Often times the PLC will refuse to open without an override which is something that maintenance is usually required to do (to keep normal ride ops from making critical mistakes).