With the addition of Longo, Josh Homes who was the former Creative Director for Halo has moved to the role of Executive Producer. The movement of Holmes could be related to some controversy that developed over a slide in a slideshow about some of the decisions that were made during the development of Halo 4. The slide, which we are not going to get into here, created a bit of a stir in the community which perhaps may have contributed to the decision.
Longo would seem to be an excellent choice as the Tomb Raider reboot was excellent and he should make a welcomed addition to the 343 team.
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