Why is that mass shooters (almost) always attack random people vs. going after people they have beef with?

I recently found out that one of my relatives was a victim in the MSU mass shooting that happened a few days ago. He’s still alive but it an extremely tenuous and horrible situation. He’s in critical condition.

The mass shooter suspect (who committed suicide) attacked Michigan State university for virtually no explicable reason whatsoever. He did have a really shitty and isolated life. That of course gives him zero justification for what he did.

However why is it that these psychos almost always harm people that they don’t know nor did anything to antagonize or harm them? It would seem like it would be more (morbidly/evil) satisfying to take out people who have harmed you in the past. Of course no one would be ever justified to commit murder out of “revenge”. But why is almost always random people?

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I obviously don’t want any sympathy for this POS. However again why is it they almost always attack random strangers vs exacting revenge against the very people they felt that have harmed them (either real or perceived transgressions). In other words if you are going to go out with a bang at least make it worth it?

Anyway I dunno wtf to make of this. So far it doesn’t appear that the shooter wasn’t ideologically nor racially motivated. But still why kill random people?
Why is that mass shooters (almost) always attack random people vs. going after people they have beef with?
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