I immediately suspected that there was a connection to the attack in Oslo. I know the difference between fireworks and gunfire. I knew what it was about," Mr Gleffe, who was described in media reports as having a military background, told Norwegian newspaper Dagbladet. "In such a situation, you don't think at all," he told Der Spiegel.
"There were people swimming everywhere in the water. I threw them lifejackets and pulled those into the boat who were having the most trouble. Everyone was screaming, but they were also helping each other."
Mr Gleffe brought his boat as close to the shore of Utoya island as he could and kept an eye out for Breivik - whom he had earlier spotted through his binoculars.
He was initially puzzled as to why some of the youths were frightened of him when he tried to rescue them, with some screaming' don't come too close' or 'do you want to kill us', but later found out that Breivik, while dressed in a policeman's uniform, had called the youths to come to him before he fired on them.
Mr Gleffe made about four or five boat trips and pulled up to 30 people out from the water. Together with other campers, they rescued a total of 150 people from the island.
