Technically no one killed him since the death was erased from the timeline by Stewie, however, since the "Who" wasn't the focus of the episode they never had anyone killing him, it was juts a randomly driven car.
Brian the Bachelor
Brian Griffin
A Woody
Brian died November 24th 2013, in the 6th episode of Season 12 | Life of Brian.---In the 8th episode Christmas Guy that aired on December 15th 2013, Stewie altered the time line and Brian was never hit & killed by the car, thus returning to the show.
Brian
Steve Callaghan said they decided to kill off Brian to shake up the dynamic of the show.Naturally Brian was saved from being killed by the car in the episode, Christmas Guy.
Brian the Bachelor
Brian Griffin
No.
Brian Does Hollywood
Brian the Bachelor
A Woody
Brian the Bachelor (Season 4)
Brian has a liberal political philosophy
Brian: Portrait of a Dog
Brian & Stewie's Emmy appearance & performance wasn't part of any Family Guy episode.
Family Guy