Brad Snider was a former bank robber and an associate of Michael De Santa and Trevor Philips. He was killed during a standoff with police during a botched bank heist in 2004, during the mission Prologue. Even after his death in the first mission, Brad's whereabouts are a major driving force in the game's story, leading Michael and Trevor to discover his body during the mission Bury the Hatchet.
This myth originated in August of 2017. It has been primarily associated with clickbait YouTubers, a fact that has put the validity of the myth into question. Still, some genuine myth hunters still investigate the myth. They cite the fact that Brad was a major character in the game as well with other paranormal encounters in North Yankton as proof that his ghost could be real.
The hunt for Brad's ghost began at the Ludendorff Cemetery, his final resting place. Brad's grave was disturbed during the mission Bury the Hatchet, which may have acted as an impetus for his ghost to haunt the area. In addition, Brad's corpse no longer spawns in the disturbed grave after the mission is completed, a possible reference. However, some users have put forth a theory that the ghost in Ludendorff's cemetery is not Brad, but one of the many other deaths associated with North Yankton: the heist crew's getaway driver (shot in the head during the escape,) Smithers and another unnamed security guard (killed during the heist,) police officers, or Triads (killed during the mission Bury the Hatchet.) In fact, if Michael is killed in Option B, it may be his ghost since the tombstone has his name on it. None of these alternative claims have ever been proven and remain on the fringe.
In December of 2017, the hunt switched mainly to the farmhouse where Brad was killed. This is because, in real life folklore, ghosts haunt the places where they die, not where they are buried. There may be some truth to this, as a video by myth hunter DaviDustin showed Trevor reacting aggressively towards an invisible pedestrian. This same behavior of the player speaking with another person who isn't there is common in other haunted locations, so this is strong evidence in favor of the ghost.