This is also the case in Norway and very strictly so. Aslak Sira Myhre tells us at The Guardian how every single terrorist attack in Norway has been from the extremist Right:
For decades, political violence in this country has been almost the sole preserve of neo-Nazis and other racist groups. During the 1970s they bombed leftwing bookstores and a May Day demonstration. In the 80s two neo-Nazis were executed because they were suspected of betraying the group. In the past two decades, two non-white Norwegian boys have been died as a result of racist attacks. No foreign group has killed or hurt people on Norwegian territory since the second world war, except for the Israeli security force Mossad, which targeted and killed an innocent man by mistake on Lillehammer in 1973.
Don't forget Gladio: Gladio (or whatever other name) was and still is the shadowy network that maintains the Empire in Europe by means of targeted killings and psy ops. It was formed out of, essentially, fascists by the CIA and MI6 after WWII but it became highly notorious in the years of lead of the 1970s and 80s.
It is very likely that this attack is one of such psy ops, even if we are yet to know why.
I insist that following the thread of the police chiefs who disabled the reaction capability should bring the research somewhere, because extremist fascist networks are invariably connected deep within the police and secret services.