Marco de Haro was a Mexican drug trafficker who served as drug lord Pablo Acosta's lieutenant and head of security till the drug lord's death in 1988.
In 1986, Acosta suspected Lili Arévalo of stealing from their shipments. Marco, without his boss's authorization, killed Lili, triggering a feud between Acosta and Lili's father Fermín Arévalo. Fermín sent a sicario after Acosta, but Acosta escaped with minor injuries to his ear. Acosta, de Haro and Amado Carrillo Fuentes kidnap the sicario while he recovered in a hospital, and de Haro tortured till he revealed it was Fermín who sent him for $1000. Acosta gathered weapons and a crew of bodyguards, and took de Haro and Carrillo to Fermín's ranch. Antonia, Fermín's wife, confronted them, and lauded Acosta's bravery for bringing de Haro to her house. She told them that Fermín wasn't there.
Fermín and his men later ambushed Acosta. de Haro and Carrillo Fuentes protected their boss, however, Fermín managed to sneak up next to Acosta and fired at him, wounding Acosta. He is killed by Carrillo Fuentes before he could finish Acosta.
Later in 1988, Acosta spoke to an American journalist about the Guadalajara cartel's corruption; which put him on the crosshair of the Mexican and American government. Marco de Haro accompanied Acosta as he began making a last stand at his fortress in the town of Santa Elena. The FBI and the MFJP raid the village, forcing Acosta and de Haro to hide in an abandoned house. Mexican policemen surround the house, but DEA agent Walt Breslin ignores orders from the Mexicans and walks into the house, only to be held at gunpoint by de Haro. Breslin convinces that he'd act as a human shield in the hopes of smuggling Acosta into the United States where he could rejoin his girlfriend Mimi Webb Miller and live under witness protection. However, Acosta changed his mind after exiting the house, and grabbed Walt's gun and lunged at the policemen, and was shot to death.