Lars was orphaned when he was eight years old by a horrific car accident which claimed both parents as well as the occupants of the other vehicle. Lars should not have survived, but somehow was "thrown clear" of the vehicle and was found thirty feet away still buckled into his car seat, completely unscathed.
His remaining known family was in Europe and lacking any other care provider stateside, Lars was briefly held in a Child Protective Services run orphanage while attempts were made to contact his European kin. A week later a tall, stern looking man named Hans Sors arrived bearing various papers to prove himself a second cousin of Lars, and claiming to represent the family's interests in the US. He took custody, and Lars departed with his previously unknown distant relation. Cousin Hans lived in Berkeley, Ca and claimed to be a professor of "advanced parapsychology" at the University. And though Hans never seemed to actually teach any classes on the campus, "students" would periodically come by his townhouse for "individual instruction". Hans was ill-suited to raise a young boy but did not shirk the responsibility; Lars was enrolled in a prestigious private school and was well provided for. Lars understandably suffered from emotional trauma and Uncle Hans was particularly good at helping in this area, proving to be a skilled therapist.
By the time he was ten Lars was sufficiently recovered from his ordeal and Hans deemed him ready to begin his apprenticeship. Slowly, carefully, Hans peeled back the masquerade of mundane reality and began Lars' indoctrination into the mystical arts. Eventually all was made known and Lars learned that he is a member of not one but two separate families that are each part of a larger cabal of interrelated family lines of Spellbinders, with a provenance rooted in ancient times. Lars is of the Kenning and Sors houses specifically and was born with a strong natural gift for magic, but neither of his parents had an active magical talent. As the two houses have a long and mixed history of rivalry and broken alliances, his parents joining was a Romeo and Juliet like case of star-crossed lovers defying familial feuding. They had departed Europe to put distance between themselves and their difficult kin. Finally Hans revealed to Lars that he had not survived the car accident that killed his doomed parents by chance but rather had instinctively channeled raw magic to translocate himself to safety, proving an impressive talent for the art.
That alone would be enough of a dramatic origin for most people, but there was more. Hans also revealed that he himself, like many of the Sors family, was a member of an esoteric order called the Societatis ex Monstrum Interfectorum that focused on dealing with dangerous supernatural threats, and he intended to train Lars to one day take his place in the secret society. Lars had little say in the matter, and thus his apprenticeship and training began. Hans proved to be a hard but fair taskmaster as he carefully honed Lars skills for the next twelve years, weaving the training around a life of academic pursuits as Lars continued his schooling. On the same day that Lars graduated with an accelerated Masters degree in Library Sciences, Hans also deemed Lars a journeyman Spellbinder and sponsored him for induction into the Societatis ex Monstrum Interfectorum as an Interfector...aka a Hunter. Thus Lars' adult life began.
Hans has recently been making noises about retiring both from his mundane life returning to Europe, leaving Lars to continue the work of the Societatis, and seems to mean it. He's recently sent Lars out into the world with orders to seek out and deal with some significant supernatural threat on his own to prove himself capable, and then return for further instruction. Lars is reluctant but determined to not let his uncle down.