An interesting example of 'a colonial avenger, once removed' or 'an evolved colonial avenger' in Canada.
By all appearances very different from Brian Steven Smith, but really just a step or two more 'melting potted'. This kind of killing lets a person 'stage' the society in which it occurs, guess where that society is in terms of melting pot development. The United States would still be decades away from that sort of crime if not for its baggage.
The colonial avenger is a melting pot archetype, and exists to some extent in all melting pots. In any forced assimilation, each person who either supports the assimilation or 'consumption' of the conquered culture, or is not aware of the variance in cultures and believes 'all people should be the same' will have some signs of this melting pot archetype. It's an essential part of any successful melting pot.
The colonial avenger is the 'retreating wave' or 'second military wave' of failed colonization efforts.
Colonizing usually has military, religious and other elements, but once the overt military stage has passed, another group of 'second string soldiers' continues a sort of guerrilla campaign against vulnerable survivors.
Brian Steven Smith is an extreme example of the Colonial Avenger.
He was raised in South Africa, a country with an extensive colonial history.
In later life he moved to the United States and married an older woman who had been an employee of U.S. immigration police and who shared his sentiments about European superiority. The marriage appears to be 'opportunistic' at best, and probably revolved around racial fears.
He 'served' in the military in South Africa and most likely considered killing 'inferiors' an extension of his military past.
Like many of the 'shooter' archetypes, he targeted people who he knew he could 'beat' or conquer. But unlike the similar shooters, he was fighting a retreating battle. Colonial Avengers are like retreating soldiers leaving scorched earth. They know they have lost but they want to exact a price, they leave deliberate footprints that their colleagues will recognize. Young shooters often want to lead a battle, they believe they are creating a path forward, but the Colonial Avenger is conquered him or her self, and is acting more on personal motives.
It's important to understand that, like most or all melting pot archetypes, the Colonial Avenger is not a new creation but simply a distortion of healthy motives.
There are many circumstances under which a person can properly attack, even circumstances under which it might be appropriate to attack for racial or cultural reasons, but the Litmus test for legitimacy is whether a reciprocal attack would also be accepted and understood as a 'signature' of supremacy.
In the case of Brian Steven Smith, he would have seen such an attack by the targeted groups on his group as having been evidence of their inferiority. In other words if a South African or North American indigenous person had demonstrated some superior skill using some weapon their skill would have been admired, but if they had been slaughtering people, particularly women, of his specific European background, it would have been 'part of their defective or criminal nature'. But, identifying as a soldier, he believed he was acting on behalf of his population under the basic 'moral authority' of supremacy, the common authority used by gangs and uniformed services all around the world.
The OAS, 'Organization of the Secret Army' is another example.
France had 'conquered and colonized' Algeria, but because many indigenous Algerians had survived and kept their language, the French were eventually forced out. The retreating Colonial Avengers tried to extract a fierce price from their 'disobedient' colony. Still today there are many French who refer to Algerians as savages. It's not unusual for an old Frenchman to tell stories about, for example, Algerians cutting off the genitals of captured soldiers, and similar acts. These 'atrocities' were probably a response to earlier atrocities committed by the French, but were used by Colonial Avengers to justify bloody acts.
Similarly, Britain still has an extensive network of foreign colonies and pseudo colonies, which they will continually find 'charitable' reasons to 'keep', but which will likely lead to hostilities which will polarize Britain itself into 'indigenists' and 'expansionists' or Colonial Avengers.
The United States is still, culturally, a de facto British Colony. Numerous European countries were involved in the initial colonization, but in the last century Britain has stepped in front to attach itself to the fortunes of the U.S., probably not a wise move.
When various African colonies fell, it was generally Britain, and British soldiers, who were the public face of attempts to 'punish' colonized people. A large number of private, or mercenary, militants from the U.K. were employed very visibly as 'Colonial Avengers' across Africa. Even as far as the Seychelles there was a very public British face to western efforts to 'punish' former colonies.
As Asia becomes more powerful, pressure will grow on the U.S. to 'settle territorial differences' with indigenous populations.
Historically the U.S. has been somewhat dishonest in the 'assistance' it gave indigenous people, much of the assistance was, in fact, merely traps, sabotage designed to weaken indigenous sovereignty and force further assimilation.
The U.S. is developing a cadre of Colonial Avengers, some of them outside of government, such as the Northwest Front and numerous paramilitary groups.
But many of them also carefully entrenched in the U.S. government, protected by a complex 'legal' infrastructure meant to postpone colonial reckoning, meant initially to protect 'colonists' until a long term sustainable solution was reached.
Britain has carefully tried to postpone its own colonial bill by supporting Australia and the United States as 'Original' or Native entities, and a case could be made that their motives are decent, but regardless it looks to be a massive catastrophe in the making.