The unnamed narrator of My Thoughts on Mackenzie Weaver gives very little information on himself, other than that he grew up in Rhode Island and attended college out of state. Given that Mackenzie Weaver died in 2013, it can be assumed that the narrator's friend, and by extension the narrator himself, would have been born in or around 1995.
The narrator tried to avoid his unnamed friend throughout college, though they always ended up meeting, with the friend giving the narrator some conspiracy theory to think about. At an off-campus party, the friend told the narrator about Mackenzie Weaver: a girl who killed several classmates with a sword in 2013. The narrator was intrigued by the fact that she used a sword, rather than a gun, and asked for more information despite his usual dubiousness. The friend explained that Mackenzie was killed by the police.
Over summer vacation, the narrator began researching Mackenzie Weaver, and discovered she was alleged to be pregnant at the time of her massacre. Mackenzie's boyfriend had turned up dead at a different college in 2014, leading conspiracy theorists to believe she came back to life. The narrator began believing in the urban myth, even becoming paranoid about Mackenzie coming to kill him.
One night, the narrator's friend appeared at his house in Rhode Island and took him for a drive, revealing he had been one of Mackenzie's surviving classmates. Mackenzie appeared and killed him, though she let the narrator escape. He spent the next year trying to recover from seeing Mackenzie, and the next summer, took a trip to her hometown, where he saw her headstone inscribed with the Mackenzie verse.
The narrator is originally dubious of his friend's conspiracy theories, purposefully avoiding him as "[not] the kind of guy it's easy to have a conversation with." However, he takes particular note when his friend tells him the story of Mackenzie Weaver, and, over summer vacation, becomes more convinced she really came back to life, even becoming scared and paranoid enough to sleep with the lights on. After seeing Mackenzie in person, the narrator becomes convinced she is a supernatural force, as opposed to an imposter, though he still frames his story as just giving the facts and allowing the reader to draw their own conclusions.