He was convicted of attempted murder while he was very well alive. He was also charged for many other crimes for two decades, the charges just never stuck because he intimidated the witnesses. Plenty of information about his deeds was recorded prior to his killing.

Whoops, I goofed. This stuff is pretty well documented actually. I look like a conspiracy theorist now.

His criminal record should clear up doubt.

But the town police colluded with the vigilantes!

How can it be certain that the record isn't a post hoc fabrication. Or if not entirely, then at least embellished.

Looking the other way is quite different than planting evidence.

Nor feasible in this case. Even a town sheriff wouldn't be able to modify offline (1981) databases of multiple jurisdictions. Or have the endurance to manufacture plausible entries and histories for dozens and dozens of cases over decades.

A few hours research could likely pierce any misinformation.