No.
Lack of success with girls is not an isolating issue.
Look at Ted Bundy.
And there are heaps of 18 yo's out there with no sex life who are not going to shoot up their local community.
This Forum is evidence of that.
It's the integration of a number of issues which simultaneously form a perfect storm.
1. Media indulgence and saturation of mass shootings
2. Some type of fantasy to kill a person(s).
3. Access to Semi Automatic guns
4. Autistic spectrum-like lack of social integration
5. Testosterone build up to ultra-violent levels
Although most of those are related to young male behaviour, I firmly believe that (1) is the primary cause now.
Mass Shootings and massacres are contagious and the media is the agent spreading this disease.
https://theconversation.com/more-mass-shootings-are-happening-at-grocery-stores-13-of-shooters-are-motivated-by-racial-hatred-criminologists-find-183098These young men are now researching each other.
13% of all mass shootings are in supermarkets.
I never think of that when I buy groceries.