That doesn't excuse their actions, nor excuse them from the "rightful" punishment.
Those Norwegian soldiers are trained and paid by the government to perform their duty as soldier when the country will call them to action.
Their duty means to kill enemy combatant, no surprise that those soldier are proud of accomplish their mission and finally pay back the country for years of investment in them.
This is the correct reading of Major Kristian Simonsen 's words "I have deployed my forces with the intent to kill, and that has been a successful choice. [...] I don't reflect much over the fact of having taken someone's life. They chose for themselves to enter the battlefield with the intention to kill us, so then we're equally good. We are two parties in a war"
the next quoted sentence is also very clear to understand:
"It was fantastic when I heard that we probably have killed the Taliban-leader who made the road bomb [IED] that killed Jokke [Norwegian soldier killed not too long ago]."
One of the enemy leaders who's action caused the death of a comrade got his retribution.
Is there any reason to be sad about it?