OSLO, Norway — When the blond man in the police uniform started firing his assault rifle, many of the youths couldn't believe it was real. It had to be a sick prank. Something this crazy could never happen in quiet, sensible Norway.

Then terror flared in the eyes of friends with a better view: of teens and young adults crumpling to the ground, blood streaming from point-blank bullet wounds. Hundreds turned and ran to every corner of Utoya Island. They opted to cower silently or swim for their lives.

One day after a gunman posing as their protector killed at least 85 campers at a youth retreat for Norway's ruling Labor Party, survivors and the local boatmen who helped save them recounted their two hours of horror, confusion and fear.

3:30 p.m.:

Three days into their annual summer camp, some 600 Labor Party youth activists from all over Norway hear the first, vague news of a bombing in the capital, Oslo, some 20 miles (30 kilometres) away. Far too distant to see billowing smoke or hear sirens. No way to tell how bad the explosion, just four minutes before, might be.

For some, a main concern is whether the camp will continue, and whether Prime Minister Jens Stoltenberg will still visit their lake-locked retreat that weekend.

4:30 p.m.:

As footage of destruction and news of deaths confirm the huge scale of the Oslo explosion, Utoya's campers gather in worried huddles and talk quietly at tentsides, in the cafeteria, at fir-lined coves and the island's tiny harbour. They touch foreheads while watching news on their smartphones. Those from Oslo call parents and siblings to confirm they're all right.

"We consoled ourselves that we were safe on an island. No one knew that hell would break out with us too," one Oslo Labor activist, Prableen Kaur, writes on her blog the next day.

5 p.m.:

Amid the coming and going of several small boats, a lone policeman arrives.

The officer -- armed, unusually, with two firearms visible on his hip and shoulder -- says he's there to boost security. To ensure they're safe.

Then, witnesses say, he raises his assault rifle and opens fire with bursts of automatic fire. His hunt of defenceless left-wing political activists has begun.

5:10 p.m.:

At the camp's food hall, Jorgen Benone is still talking with friends about the Oslo attack as they "hear panic down by the water."

"We were wondering: What's happening? Is it some balloons exploding or is somebody kidding?" he says. "Then we started to understand that people actually had been shot. Chaos broke out everywhere, and everyone started to run."

People at the camp report trying to call Norway's emergency services but are told to keep off the line unless they're calling about the Oslo bomb.

5:15 p.m.:

Witnesses say the gunman enters a village of tents, the residential heart of the weeklong retreat, and spots desperate individuals hoping he'll spare them if they run back inside their homes. But the killer is seen working his way tent by tent, shooting many point-blank, one by one.

5:20 p.m.:

Kaur joins a group of panicked, confused campers. They are running from the approaching gunman, his "POLICE" moniker crystal-clear to see from even middle distance.

"My first thought was: Why are the police shooting at us? What the hell?" she writes.

More than a dozen crowd into a dark corner of a camp building, and all lie down on the floor. She cries quietly -- then sees her best friend from camp, a boy, through a window.

"I wondered if I should go out and bring him to me. I did not. I saw fear in his eyes," she writes.

5:25 p.m.:

Kaur says a burst of gunfire extremely close to the building triggers panic and the entire group leaps out of a far window. Several suffer injuries, including a girl with a broken ankle, but the shooter doesn't immediately pursue them. She takes new cover behind a low brick wall, telephones her mother on her cellphone, and sends a text to her father.

"Many were there," she writes. "I prayed, prayed, prayed. I hope that God saw me."

5:30 p.m.:

As the gunman picks off lone campers who run from their hiding spots as he draws near, many find themselves at the shoreline with only one apparent escape route -- the water.

Kaur says the gunman tries to draw out the hiders near the brick wall, shouting, "I'm from the police!" Campers shout back, "Prove it!" He shoots at those who move. She lies still, on top of the legs of a teenage girl covered in blood.

5:38 p.m.:

Police say an armed SWAT team is deployed from Oslo. They drive rather than take a helicopter, police say -- because the chopper would take too long to prepare for flight.

5:45 p.m.:

At another camp site on the mainland shore near Utoya Island, camp owner Brede Johbraaten has been listening to the sound of gunfire -- sometimes lone pops, other times staccato bursts -- waft across the humid evening air for more than half an hour.

But it's only now that he discovers the horror unfolding some 800 metres (yards) of frigid water away.

The first survivors, among the strongest and luckiest, have swum the full distance. They aren't wounded but say many of their campmates are dying in the water behind, some bleeding to death from bullet wounds, others cramping up and drowning.

Johbraaten, 59, and other campers rally several small craft to join a local flotilla converging on the island from several points, including another island to the north. They pluck both flailing swimmers and lifeless bodies from the surface.

"It was hard for some of these youngsters to swim a distance of 800 metres under these conditions," Johbraaten said.

Amid the chaos, the arriving police SWAT team complains that no boats have remained on shore as they'd expected, compounding the delay.

6 p.m.:

Witnesses lying low behind rocks, aware that the "policeman" is really the threat, watch helplessly as four campers run to the officer for help -- and are each killed with shots to the head.

6:20 p.m.:

Police say the SWAT team finally reaches the island and fans out, still unaware of how many gunmen they're trying to find.

Benone has remained behind the same boulder, trying not to move.

"I felt it was best not to sit quietly, not to run in the open because then he could see me. ... I thought of all the people I love, and how I just wanted to go home."

6:35 p.m.:

Police say they find the gunman and order him to lay down his weapons. He complies and is arrested.

Around this time, Kaur says she finally plucks up the courage to stand up -- and sees that she's been lying on a lifeless teenage girl: "My guardian angel," she calls her. She jumps into the water to join a group of campers clinging to a large innertube. A passing rescue boat throws them all life vests but is too full with other rescued campers and can't collect them too.

7 p.m.:

The private rescue flotilla continues to circle the island in search of survivors. The boats come closer now that the shooting has stopped. Kaur is scooped from the water. But many campers fear leaving their hiding spots.

Benone sees several boats approaching but wonders if these rescuers might be killers, too, and hesitates.

"I didn't know if I could trust them. I didn't know who I could trust anymore," he says. "But I started waving and jumped into the water. I was crying, that's how happy I was. But I was so cold. Ice cold."