OSLO, Norway — Police arrived at an island massacre about an hour and a half after a gunman first opened fire, slowed because they didn’t have quick access to a helicopter and then couldn’t find a boat to make their way to the scene just several hundred yards (meters) offshore. The assailant surrendered when police finally reached him, but 82 people died before that.

Survivors of the shooting spree have described hiding and fleeing into the water to escape the gunman, but a police briefing Saturday detailed for the first time how long the terror lasted — and how long victims waited for help.

The shooting came on the heels of what police told The Associated Press was an “Oklahoma city-type” bombing in Oslo’s downtown: It targeted a government building, was allegedly perpetrated by a homegrown assailant and used the same mix of fertilizer and fuel that blew up a federal building in the U.S. in 1995.

In all, at least 89 people were killed in the twin attacks that police are blaming on the same suspect, 32-year-old Norwegian Anders Behring Breivik. . .