Edward Bunker was a novelist and screenwriter who had served significant time in California prisons — including San Quentin, where he had known Trejo. He had published crime fiction, most notably No Beast So Fierce (1973), which had been adapted into the Michael Caine film Straight Time (1978). By the mid-1980s, he was working as both a writer and an actor — he appeared in Reservoir Dogs (1992) as Mr. Blue — and he was connected to the film world in ways that Trejo, at that point, was not.
Trejo came to the Runaway Train set not to act but to help. A young person associated with the production was struggling with cocaine use, and Trejo was called because of his work as a substance abuse counselor. He showed up. He did the thing he did — talked to the person, offered the perspective of someone who had been through it, tried to help.
Bunker was on set. He recognized Trejo. He knew Trejo’s boxing background from their shared time in the California prison system. He told the director, Andrei Konchalovsky, about Trejo.
Konchalovsky needed a boxing trainer for the film — specifically, someone who could work with Jon Voight on the physical and psychological presentation of a prison boxing background. Trejo had the background. He was hired as a boxing trainer, which brought him onto the set in an official capacity. And then, because Konchalovsky was working on a film about prison life and had a man with direct experience standing in front of him, Trejo was offered a role.