A 4-year-old boy is home and doing fine after he fell into a gorilla enclosure at the Cincinnati Zoo on Saturday, but some animal lovers and activists are questioning the zoo's decision to shoot and kill the gorilla to save the boy's life while a petition is even calling for the boy's parents to be held responsible for the animal's death.

Zoo personnel shot and killed Harambe, a 17-year-old mountain gorilla, after the boy fell into the enclosure and was grabbed and dragged by the animal, who seemed to act alternately protective and aggressive toward the child.

And on Monday, the woman who captured the video the incident that went viral, said she overheard the boy say he was going to breach the barrier and enter the enclosure.

"I heard the exchange while I'm waiting. 'I'm going to go in.' 'No, you're not.' 'I'm going to go in.' 'No, you're not.' The mother turns around to her other children," Kim O'Connor said.

Zoo director Thane Maynard regretted the endangered ape's death, but  he said "the right choice was made."

Maynard said "the right choice was made" but expressed remorse that the Western lowland silverback, a critically endangered species, had to be killed.

"The zoo's in the business of taking care of endangered animals, and we don't want to be in the situation in which they have to be killed," Maynard said. "Harambe was a good guy."

People for the Ethical Treatment of Animals (PETA), which maintains that animals should not be kept in captivity in the first place, also criticized the zoo for not having a second protective barrier between the gorillas' home and the public.

"Even under the 'best' circumstances, captivity is never acceptable for gorillas or other primates, and in cases like this, it's even deadly," the organization said in a statement. "This tragedy is exactly why PETA urges families to stay away from any facility that displays animals as sideshows for humans to gawk at."

However, some well-known animal experts applauded the zoo's actions, despite the unfortunate loss of the beloved primate.

"They cannot tranquilize it. It takes five to 10 minutes," said Jack Hanna, director emeritus of the Columbus Zoo, also in Ohio, and a well-known TV personality. "We are all sorry. All of us in the zoo world are heartfelt for this thing, but thank goodness a human being is alive today because the decision the Cincinnati Zoo made."

The incident came about a week after zoo staffers in Chile shot and killed two lions to save a man who had entered their enclosure and stripped off his clothes.