Hoodie is the fan-given nickname of a hooded character in MarbleHornets, first appearing in Entry #41. Not much is known about him until close to Entry #83, and even after the end of the series, many questions remain. Hoodie has been seen in several entries, the first time in Entry #39 where he first appears, stalking Jay while he sleeps in his car. In Entry #61, Hoodie is confirmed to be at least one of the people posting to the Totheark account.

During Entry #83, Tim attacks Hoodie, causing him to fall from a windowsill, seemingly killing him. Tim collects a tape from his pocket, which is shown, during Entry #84, to be the footage of Alex's auditions for Marble Hornets before he encountered The Operator. Brian is shown to be wearing the same hoodie during the auditions as Hoodie always wore, leading Tim to believe they were one and the same. This theory was later proven to be true in Entry #86, which also confirmed that Hoodie was indeed killed by the fall. In an interview for MarbleHornets, Troy Wagner, Joseph DeLage, and Tim Sutton confirmed Brian to be Hoodie.

https://theslenderman.fandom.com/wiki/Brian