I don't know why the article focuses so much on "the first X months." From 2010 through 2019, Norway had 298 victims of murder,[1] so 29.8 per year, or 2.5 per month, in average. Things usually "heat up" during the summer when more people are out and about.

[1] https://www.politiet.no/globalassets/04-aktuelt-tall-og-fakt..., excluding the 2011 terror attack.