I think it was more like 45 minutes, but I’ll admit that can sure seem like hours when a bunch of people are taking potshots at you during that time.
Ok, looked it up. The Columbine shooting began at 11:19 and the SWAT team didn’t enter the school until nearly two hours later at 1:09 and didn’t get to the library until 3:22 (that was the 4 hours - if only they’d been quicker). I’d say the Norwegian police did a bit better. Not much, but they did have to get out to an island compared to just down the street. As another poster said, when seconds count the police are hours away.
http://en.wikipedia.org/wiki/Columbine_High_School_massacre