Jason Harris was a young human hunter who hunted Stefan Salvatore, believing he had killed his sister, Joanne. However, he was mistaken as it was Damon, Stefan's brother, who killed her. Before Jason shared an identical fate, he would later be saved by Stefan Salavtore.
Jason introduced himself on a video camera, giving the reason why he was hunting Stefan Salvatore: because he was the vampire who killed his sister Joanne (not to mention that she was turned into a vampire). He went to Mystic Falls and in the Mystic Grill, he talked to a waitress about the Salvatore Boarding House. She told him that the owner Zach Salvatore had thrown everyone out and closed the boarding house three months previously due to the arrival of family (Stefan). Jason went back to his car and opened the trunk, checking to see if he had everything he would need: garlic, holy water and a crucifix.
Jason took his video camera and went to the Salvatore Boarding House and snooped around Stefan's bedroom. He put the crucifix in front of Stefan's door, garlic in his clothes and holy water on his bed. He found Stefan's journals and read a passage from one of them. He mistakes Stefan's writing about Elena and believed that Stefan was hunting her. He vowed he wouldn't let Stefan hurt anyone else and planned to kill him.
From in the bushes, Jason was shocked to see Stefan jump from the boarding house roof. He couldn't understand why his traps didn't work and why Stefan could go in the sun. He started to doubt whether what he believed was true until he came across rabbits drained of blood. He continued to search for more until he came across two dead bodies in the same condition as Joanne was found. He was horrified by the sight and knew he had to stop it.
He went back to Stefan's bedroom and found that it was still empty. He decided the only way to destroy a vampire was to destroy his home. He becomes spooked by a crow by the window and the window mysteriously opening. In the shadows there was a tall thin figure and Jason realized Stefan wasn't the person that killed his sister. It was revealed to be Damon Salvatore. As Damon chokes Jason and drops him to the floor and picks up Jason's camera, Damon tells the dying man to say hello to the people of Mystic Falls and to say goodbye as he turns off the camera.
However, before Damon could kill him, he was forced to speed out of the Salvatore House when Stefan and Zach got back and found Jason, who was nearly close. After been healed by Stefan's blood, Jason explained the whole story about his past and what happened to his sister. Since there was no vervain in his system, Stefan was forced to compel him to forget everything that happened to him and leave town for good.