Ten years ago, Norwegian far-right extremist Anders Behring Brevik killed 77 people, many of them teenagers, in a bomb attack and gun rampage. The July 22 attacks left Norway, a small, close-knit Nordic country, stunned and grieving. Just over a year later, Breivik was sentenced to 21 years in prison, the maximum possible term. And Norway, led by then-Prime Minister Jens Stoltenberg, came together in a show of unity in the wake of the deadliest violence seen there since World War II.

A decade on, the anniversary will be an occasion of great sadness for many in the country of just over 5 million people. Several commemorative events are taking place Thursday in the capital, Oslo, and on Utoya Island, where the attacks took place. At a televised memorial concert, King Harald said lessons could be learned.

"Certain dates are written into our country's story as defining days. Days, which in different ways, have contributed to making us who we are today. At the same time, we must acknowledge that we as a society have not done nearly enough to see, to help, to carry the burden together - and to counteract the dark forces," he added.

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