Thor Langli says initial reports suggested there were two suspects and two more bombs due to go off in Norwegian capital
A police official has described how an explosion outside the government headquarters in Oslo caused chaos, allowing the bomber, Anders Behring Breivik, to slip away to Utøya island where he shot 69 people.
Eight people were killed by the Oslo bomb. Breivik, a rightwing extremist, has said he thought he would be killed by police before reaching Utøya.
Testifying in Breivik's trial, police operations leader Thor Langli said initial reports after the blast suggested there were two suspects, and two other bombs were about to explode.
Langli recalled standing next to the head of an anti-terror squad in Oslo when he received a call about the second attack at the Labour party's youth camp on Utøya, about 25 miles (40km) from the Norwegian capital.
"I saw on his face that it was something serious," Langli said. "And while I was watching him he said out of the corner of his mouth: 'Shooting on Utøya.'"
Another report came in that about 50 people had been shot on the island. The anti-terror unit was dispatched to Utøya. When it arrived, about 70 minutes after the first reports of Breivik's rampage, 100 people had been shot.
Breivik testified last week that he had expected to be shot by police after the bombing. But no one stopped him as he walked to a getaway car parked near the bomb site and drove to Utøya.
"I estimated the chances of survival as less than 5%," Breivik said.
Langli said he first got a report of a suspect with a "non-Nordic" appearance leaving the scene. He then got another report of a Nordic-looking suspect, which made him believe there were two suspects.
When he heard about the Utøya shooting, he started thinking the bomb and the massacre were the actions of the same person.
"I thought there was a connection. But I didn't have any evidence for that," Langli said. Turning to Breivik, he added: "I could not imagine there being two people with so many crazy ideas."
A security guard who was in the Norwegian government high-rise building struck by the car bomb testified on Tuesday that he had barely focused a security camera on the licence plate when the vehicle exploded. Tor Inge Kristoffersen described the scene in downtown Oslo as a "war zone".
Svein Olav Christensen, an explosives expert working for a defence agency, showed pictures of the bomb site to the court. The 950kg (2,000lb) fertiliser and diesel bomb had ripped holes in the concrete platform underneath the vehicle, and also in the subterranean floor below.
Breivik has said he was disappointed when he found out that the building had not collapsed. Christensen said the bomb would have had to be "much larger" to bring down the structure.
The trial is scheduled to go on for nine more weeks.