Trond Berntsen was working as an off-duty police officer on Utøya when Anders Behring Breivik arrived at the shore. Unarmed and unaware of the horror that was about to be unleashed on the island, Berntsen succeeded in protecting his 10-year-old son but could do nothing to save himself. The father-of-two became one of Breivik's first victims when he was shot dead within minutes.

In a sign that the killing spree has left no sector of Norwegian society untouched, the royal court has announced that the 51-year-old was the stepbrother of Mette-Marit, Norway's crown princess.

"The crown princess's thoughts go to his closest family," a spokesman for the palace told Dagbladet newspaper.

As they continued to trawl through water and rubble for the missing, on Monday police said they had reduced the number of people believed to have died in the Utøya massacre from 86 to 68 – the vast majority of them teenagers taking part in a leftwing political summer camp. Eight people, rather than the seven previously stated, had died in the Oslo bomb blast, they added.

A full list of the dead and missing has not been made public. A team of nearly 40 police officers is working to identify all the bodies found so far. However, in his tearful address in the national cathedral on Sunday, prime minister Jens Stoltenberg mentioned the names of several victims known to have been shot dead while at the Labour Party (AUF) youth camp.

One of them, Tore Eikeland, was "one of our most talented youth politicians," he said; a 21-year-old local councillor and the leader of Young Labour in the south-western Hordaland region. At a recent party conference, the prime minister added, Eikeland had been given a standing ovation from the entire auditorium.

The names of other victims – both known and suspected – have been reported locally. Among those still missing yesterday was Hanne Kristine Fridtun, a 21-year-old AUF activist who had made herself known in her local town of Stryn, western Norway, for her social conscience. "I know Hanne Kristine very well. We have had a close political co-operation … so for me it is now completely unreal that she is missing," the mayor of Stryn, Nils P Støyva, told Norwegian broadcasters NRK. Fridtun had shown a touching sympathy for the least well-off in society, he added, and had recently raised awareness of the difficulties faced by disabled people in Stryn. "This is terribly hard for everyone," he said.

She was not the only one to be praised for her political commitments. Eighteen-year-old Tarald Mjelde, Eikeland's deputy who was last night missing presumed dead, was described on a blog by a friend and fellow youth activist as "the little boy with an enthusiasm that infects everyone around you." Erik Dale wrote: "All the people who wish they had your energy. Your eagerness. If you hadn't been such a great little politician, I am sure you could have been an athlete." He added: "You love your football, even if you support the wrong team. How did you end up with Chelsea anyway? Please come home safe so you can tell me. We need you."

One of the youngest feared dead has been named as Johannes Buø, a 14-year-old AUP activist from southern Norway, whose father confirmed he was missing. A Facebook page created for friends, family and well-wishers to write messages of sympathy was filling with tributes. One of them read: "Dear, dear John! It is unreal what has happened. You are an incredibly strong person … We all hope desperately to get you home safe and sound. We hope, light candles and pray for you."

Social networking has also been used to express solidarity for other missing youngsters, including 17-year-old Syvert Knudsen. Some messages were moving in their understanding of teenage troubles. "[It] is sad to think that you always said you were so lonely and that you always were so sad," wrote one friend, Tonje Fredriksen. "Wish you were home and could see how many people think of you, miss you and care. Love you … and I'm not alone."