The man in the police uniform shouted for the campers to come closer. When they did, he killed them.
The gunman who killed at least 80 people at an island youth camp northwest of Oslo used his disguise to lure in his victims, then shot them twice to make sure they were dead, survivors said in the village of Sundvollen, where they were taken after the massacre.
"I saw many dead people," said 15-year old Elise, whose father, Vidar Myhre, didn't want her to disclose her last name. She just feet away from the gunman when he opened fire in the camp on Utoya island.
Elise said she had just come out from an information meeting in a nearby building when she heard gunshots. She saw a police officer and thought she was safe, but then he started shooting.
"He first shot people on the island. Afterward he started shooting people in the water," she said.
Elise said she hid behind the same rock that the killer was standing on. "I could hear his breathing from the top of the rock," she said.
In panic, the girl phoned her parents, whispering to them what was going on.
"They told me not to panic and that everything would be OK." Her parents also told her to get rid of a brightly colored jacket she was wearing to not draw attention to herself.
She said it was impossible to say how many minutes passed while she was waiting for him to stop.
Survivors described a scene of sheer terror at the camp, which is organized by the youth wing of Norway's ruling Labor party. Hundreds of young people were eagerly awaiting a speech the prime minister was to give there today.
Police said the man arrested in the shooting is Norwegian and had set off a bomb that killed seven people outside the prime minister's headquarters in Oslo, about 20 miles from the camp.
Several of the survivors seemed calm as anxious parents picked them up at a Sundvollen hotel, but the stories they told were of utter terror.
Dana Berzingi said the fake police officer ordered people to come closer, then pulled weapons and ammunition from a bag and started shooting.
Several victims "had pretended as if they were dead to survive," the 21-year-old said. But after shooting the victims with one gun, the gunman shot them again in the head with a shotgun, he said.
"I lost several friends," said Berzingi, whose trousers were stained with blood. He said he used the cell phone of one of his fallen friends to call police.
Emilie Bersaas, identified by Sky News television as one of the youths on the island, said she ran inside a school building and hid under a bed when the shooting started.
"At one point the shooting was very, very close (to) the building, I think actually it actually hit the building one time, and the people in the next room screamed very loud," she said.
"I laid under the bed for two hours and then the police smashed a window and came in," Bersaas said. "It seems kind of unreal, especially in Norway. This is not something that could happen here."
Another camper, Niclas Tokerud, stayed in touch with his sister through the attack through text messages.
"He sent me a text saying 'there's been gunshots. I am scared (expletive). But I am hiding and safe. I love you,"' said Nadia Tokerud, a 25-year-old graphic designer in Hokksund, Norway.
As he boarded a boat from the island after the danger had passed he sent one more text: "I'm safe."