From Halopedia, the Halo wiki
Brian Reed was the Halo franchise lead writer at 343 Industries. Previously employed by Marvel Comics, his first Halo work was Halo: Fall of Reach, a comic book adaptation of the Eric Nylund novel The Fall of Reach. He served as a writer for Halo 4 and was the lead writer of Spartan Ops. Reed later wrote the comic miniseries Halo: Initiation and subsequently issues 7 through 10 of Halo: Escalation. Reed also wrote Rossbach's World, one of the short-stories in Halo: Fractures.
Reed was the lead writer for Halo 5: Guardians, before moving to the position of Lead Narrative Director of the Halo franchise. Reed was an additional cinematic writer for Halo Wars 2. In early 2017, it became known that he had stepped down from the position.