According to current canon:
The Inquisitorius were the Galactic Empire's Jedi Hunters, trained by Darth Vader to use the dark side of the Force and to wield double-bladed spinning lightsabers as they assisted in the extermination of the Jedi.
No specific background was common among Jedi hunters; they came from diverse upbringings and species.
Numerous Jedi hunters were Force-sensitives themselves. The majority of Force-using Jedi hunters were members of Dark Side cults and groups that were traditional enemies of the Jedi, the most notorious of these being the Sith. Others were former Jedi driven to the Dark Side by unfortunate, traumatic events, and, believing their former mentors responsible, decided to pursue a homicidal grudge against the Order. Examples of such beings included Asajj Ventress, Aurra Sing, or the Sith Lord Darth Vader.