Captain Gustavo Grena (d. 29 Dec 1992) was the director of investigations with the Baja California State Judicial Police in Mexicali, and the supervisor of Lt. Carlos Aguila. He was on the payroll of drug lord Humberto Zorillo and used his position to thwart investigation into Zorillo's activities.
On 27 December 1992, he received a call from LAPD detective Harry Bosch regarding the disappearance of Fernal Gutierrez-Llosa. He immediately suspected that this could lead to Zorillo and he tried to steer Bosch away from Zorillo's shipping center at EnviroBreed. He was killed by Osvaldo Arpis Rafaelillo on 29 December 1992 just prior to an incursion on Zorillo's ranch.