A WHISTLEBLOWER SAYS HIS DREAM JOB TRAINING KILLER WHALES AT SEAWORLD TURNED INTO A NIGHTMARE, ON "WHISTLEBLOWER," FRIDAY, JUNE 7

"SeaWorld: The Case Against Captivity" - John Hargrove, a former SeaWorld senior killer whale trainer, was entranced with whales ever since he first visited the theme park as a child. But after years of working at SeaWorld, he grew to believe that the forced captivity of the whales resulted in a host of physical and behavioral issues - including aggressive and dangerous actions - and he decided to speak out and quit the job he once loved.

Host Alex Ferrer investigates the treatment of SeaWorld's captive killer whales, on WHISTLEBLOWER, Friday, June 7 (8:00-9:00 PM, ET/PT) on the CBS Television Network.

Killer whales are naturally social animals that can swim up to 100 miles a day in the wild. But Hargrove witnessed firsthand the consequences of confining them to small enclosures, which, he says, sometimes resulted in the parks having to medicate the whales to help them cope with the stress of captivity. Hargrove, who was also involved in SeaWorld's pioneering breeding program, speaks about the negative impact of separating mothers from their calves, a relationship in the wild that often lasts the duration of the mother's life.

The final straw for Hargrove came when an experienced fellow trainer, Dawn Brancheau, was killed at SeaWorld Orlando by a 12,000 pound male orca named Tilikum. Since leaving his job, he has appeared in the acclaimed documentary "Blackfish," written a book about his time at SeaWorld, and co-sponsored legislation to protect Orcas in California.

The episode also features interviews with two trainers who, for the first time, share their experiences with whales at SeaWorld.

WHISTLEBLOWER is produced by CBS News Productions and CBS Television Studios. Alex Ferrer is the host. Susan Zirinsky is the senior executive producer. Anthony Batson, Alex Ferrer and Ted Eccles are the executive producers. Peter Bull and Ruth Chenetz are the senior producers. Chana Gazit is the producer. Alicia Tejada is the senior coordinating producer. Chiara Norbitz is the field producer. Hannah Vair is the associate producer. Marcus Balsam is the series producer-editor. Maria Barrow and Libby Fabricatore are the editors.