Please, cite the text in your source article that states that Breivik murdered Christians.
I'll understand if you can't.
It does state this: Breivik chose to be confirmed into the Lutheran Church of Norway at the age of 15. Breivik believed himself to be the "knight Justiciar grand master" of a Templar organization. Breivik was characterized by analysts as being a right-wing extremist with anti-Muslim views and a deep-seated hatred of Islam, who considered himself a knight dedicated to stemming the tide of Muslim immigration.
On July 22, 2011, Breivik bombed government buildings in Oslo, which resulted in eight deaths.
Within a few hours of the explosion he arrived at Utøya island, the site of a camp for Worker's Youth League, posing as a police officer in order to take the ferry to the island, and then fired intermittently for more than one hour, killing 69, with one murder victim as young as 14 years old.
Breivik confessed and stated that the purpose of the attack was to save Norway and Western Europe from a Muslim takeover, and that the Labor Party had to "pay the price" for "letting down Norway and the Norwegian people."
Breivik prepared a document titled 2083: A European Declaration of Independence. The manifesto states its author is "100 percent Christian."
https://en.wikipedia.org/wiki/Anders_Behring_Breivik