Sergio was one of many Mexican immigrants who worked at the Parnell Soup Factory, along with Jorge Garcia Cruz. Sergio worked as a dispatcher. His main duties involved loading, unloading and arranging deliveries. However, Serigo collaborated with Jorge and became part of Ernesto Juarez's reefer distribution ring. Sergio's role was to arrange deliveries of reefer-filled soup cans to prominent distribution points such as the 20th Century Market, and even distributed it to other states.
Events of L.A. Noire
A reefer addict named Freddie Calhoun gave a tip to the LAPD's Vice Department, that ultimately lead to the exposure of the ring. Detectives Cole Phelps and Roy Earle went to the factory to investigate a link to the reefer-filled soup cans, after finding copious amounts of cans at Jorge Garcia Cruz's house. During questioning, Phelps observed Sergio fiddling with a silver dollar coin, similar to Juan Garcia Cruz's, hence correctly suspected Sergio's involvement in the reefer ring. Sergio gave up that he was part of the inside job along with Jorge. Phelps told Sergio not to warn his accomplices of their investigation, in exchange for immunity and for not being deported.