Well I mean murdering someone breaks the very definition of libertarianism so you can be very sure they're just using that moniker because it fits whatever they're really trying to accomplish.
the maximum freedom for each individual to follow his own ways, his own values, as long as he doesn't interfere with anybody else who's doing the same.
https://www.hoover.org/research/take-it-limits-milton-friedman-libertarianism
But you're absolutely right that a lot of people who are today clearly cheering for fascists used to call themselves libertarians.
Southwestern USA had drought periods lasting hundreds of years in recent history. That's normal for the region. And we think we should pack a few tens of million people there and treating ground water as infinitely renewable.
Solar power + desalination en masse or gtfo ...
https://www.mercurynews.com/2014/01/25/california-drought-past-dry-periods-have-lasted-more-than-200-years-scientists-say/