A fun-filled event billed as the "Shamu Adventure," took a shocking turn in San Antonio, Texas on Monday, when a killer whale suddenly turned on its trainer.

Thousands of Sea World spectators watched in horror for several minutes as the whale, named Ky, kept trying to dive under the water and hit its trainer.

At one point the whale even tried to take a bite out of him.

"The trainer would see the whale coming and he would go under before the whale actually hit him," said Justin Lecourias from Houston, Texas, who was watching in the stands with his family.

"He just tried to stay afloat and tried to calm the whale down as much as he could," Lecourias told Good Morning America.

"I didn't realize that something was going wrong," said Justin's wife, Crystal. "Justin pointed out to me that something was wrong because of what the whale had done."

Sea World officials tried to calm the situation by playing soothing music, but everyone watching remained stunned and shocked by what they were seeing.

"Towards the middle, I was getting pretty concerned when I saw the trainers running around and slapping the water," Justin Lecourias said.

"I told the kids to close their eyes."

The shocking incident ended when the trainer was able to jump on the whale's back and leap to safety. Lecourias said that still didn't calm Ky down.

"The whale turned around and slammed down on the ramp and went up as far as he could."

The Shamu Adventure was cancelled for the rest of the day.

Afterwards, the trainer managed to apologize to the audience for what happened, but there's no word on his injuries. Despite it all, he's already said he'll be back in the pool with Ky when the show resumes.

Veterinarians, meanwhile, believe the whale is near breeding age and somehow felt threatened.