Rex Weyler and Paul Watson, both among the group co-founders of Greenpeace, describe the danger and tragedy of the very first whale rescue mission they conducted in 1975, along with co-founder Bob Hunter. See film footage of the rescue mission that confronted a Russian whale hunting fleet that was tracking a pod of sperm whales, roughly 40 miles off the coast of California.

Watch Film Excerpt: Greenpeace’s First Whale Rescue Mission

Unsuccessful at stopping the harpooner from striking two whales, Weyler and Watson were forever changed by the experience of meeting the gaze of a dying bull whale.

Watson, founder of the Sea Shepherd Conservation Society through which he continues to hunt whale hunters, says, “From that moment on, I decided that I work for whales, I work for seals, I work for sea turtles and fish and seabirds. I don’t work for people.”

This is a film excerpt from A Fierce Green Fire. American Masters presents A Fierce Green Fire, the first big-picture exploration of the environmental movement, premiering nationally Tuesday, April 22, 2014, 9-10 p.m. on PBS (check local listings) in honor of Earth Day.