Mark Ames wrote a whole book (which I admit I didn't quite finish) with the thesis that you could tie the rise of workplace shootings to an increase in worker precarity.
(Thanks for the recommendation in any case.)
[0] https://www.amazon.com/Going-Postal-Rebellion-Workplaces-Col...
Funny, outside of the US even in countries with high unemployment nobody goes around and shoots anyone.
I can't speak for the culture of other countries, but Americans have a deep-seated sense of worth tied to profession. Having your livelihood stripped raises existential questions about whether you have any value as an American (to understand this phenomenon better, it may be worth also comparing suicide rates in the US after a job loss to suicide rates in other cultures in similar situations).
... but in addition, the US has a pretty deep-seated cultural mythos that when your worth is taken by someone, you take it back, using violence if necessary. Witness the Revolutionary War and the recent phenomenon of a conservative political group naming itself after an economic rebellion against the East India Company.