if that was the case you would expect to see a lot more mass shootings in Europe than in the States, simply based on the much stricter weapon control policies in the former.
The availability of means to gain an advantage in force (weapons, superior numbers, etc.) and environments of ensured disparate force interact, they don't exist separately in a vacuum. The history has borne this out time and time again in genocide, pogroms, lynchings, etc.
For posterity's sake, here's the full text of The Pseudocommando Mass Murderer: Part I, The Psychology of Revenge and Obliteration (PDF) in case you want to review it as I have.
just for you to have some actual research to look into
I really hope you're not implying the research I linked a few posts ago isn't actual research. It's proven very effective in saving lives, and doesn't face the severe conflicts of interest often found in academic papers, and sometimes entire journals on topics where agendas are involved. Whether it's the Joyce Foundation or the Cato Institute, the sources of funding can predetermine the conclusions and the quality of peer review, even to the point of misrepresenting sources cited. Law enforcement has no conflict of interest with finding real solutions on this topic as far as I can tell; quite the opposite.
The solutions mentioned in the Prevention section of The Pseudocommando Mass Murderer: Part II, The Language of Revenge (PDF) aren't exactly actionable in comparison.
That same section uses citation 38, which doesn't actually back up the claim it was cited for (source here). They had no issue citing the study on Australia's laws and the inferred changes, but with the US's ten times larger population sample they experience no cognitive dissonance in ignoring the number of school attacks in the 20 years preceding (9) and the 20 years following (93) the Gun-Free School Zones Act of 1990 in the US, while the number of non-school mass shootings remained the same at 25 incidents in the same time horizon preceding and following its passing. The interaction between firearms laws and mass killings isn't as simple as they imply, and conveniently in either parts of the main paper the perceived odds of success at one's objectives before death didn't factor into the analysis of the killers' psychology.
it does suggest that toting guns around won't actually solve any problems.
Someone who is seconds away rather than minutes away with the power to stop a killer can make enough of a difference to prevent the incident from escalating to a "mass killing" (four or more dead in quick succession) , , , , , , , , , .
Such outcomes are relatively rare because the population that actually carries that power and responsibility with them on a daily basis is currently about 3%, but despite approval from their state to carry in public, in most states licensees are nonetheless limited by laws that forbid them from carrying in many places, including those most often targeted by modern mass murderers. In the examples provided, many of those people broke the law in order to save lives, and were likely doing so on a regular basis before the fateful day came.