The pilot had been operating the hot air balloon for several hours and was providing tethered flights to passengers at a fairground during a night event. The pilot described that at the conclusion of a several minute flight, he would land and exchange passengers. To maintain the weight of the balloon during the passenger exchange, one passenger would disembark and then would be replaced by a boarding passenger. There were also several (volunteer) ground crewmembers who would keep their weight on the balloon’s basket and help control the flow of passengers in and out of the basket. Shortly before the accident, the pilot was assisting a passenger with boarding when two passengers unexpectedly disembarked. The balloon suddenly started to rise, and the pilot yelled, “clear, watch the ropes,” which was the signal to the ground crewmembers to take their hands off the basket and to make sure that none of the exiting passengers got caught in the tether ropes. As the balloon rose, the pilot felt a shake, and when he looked over the side of the basket, he saw one of the ground crewmembers lying on the ground. One of the passengers described that when she stepped off the balloon, it began rising. She saw a ground crewmember hanging on the outside of the basket as it climbed. When the balloon reached about 15 to 20 feet above the ground, the ground crewmember let go. The ground crewmember was seriously injured during the fall.