Crew Chief Cullen was a member of the UNSC navy and served as a crew chief for Pelican dropships. In 2552, he was assigned to the UNSC Pilar of Autumn and Pelican Echo 419 under Captain Carol Rawley. The job of a crew chief is to make sure all ordinance in the storage bay is secure before the ship lifts off.
When the Autumn arrived at Installation 04 and was shot down, Cullen went with Foehammer and Lieutenant Frye to the Pelican and launched it as the ship was going down, effectively saving it from destruction. Cullen likely flew with Foehammer on all the missions durin The Battle of Installation 04 and was likely killed when the dropship was shot down during the final moments of the battle.