WASHINGTON — (CNN) Brittney Sparks didn’t plan on telling her young daughter what happened to a silverback gorilla at the Cincinnati Zoo.

But they were visiting from Kentucky and MacKenzie, 5, saw something on the news and asked about it.

This wasn’t how Sparks wanted her daughter to learn the lesson of what happens when children wander, but she answered the girl’s question the best she could.

“I kind of gave the general, ‘the little boy fell in and the gorilla was doing what gorillas do, he wasn’t trying to hurt him, but he was so they had to kill the gorilla to save the boy,'” Sparks told CNN.

Sparks, her daughter and 2-year-old son Brody came to the zoo on Tuesday, the first day the gorilla exhibit reopened to the public.

Zoo officials shot and killed a 450-pound gorilla named Harambe 10 days ago after a 3-year-old boy breached the previous barrier, scrambled through thick bushes and dropped into the moat surrounding the enclosure.

The gorilla grabbed the boy and pulled him across the moat through the water.

Zoo officials who feared for the child’s life made the decision to shoot the animal.

Sparks said it was an “unfortunate” way for her daughter to learn what can happen if you don’t stay close to your parents.

“I talked to her about how important it is to stay with me and not wander off, because accidents do happen,” she told CNN.

Tuesday’s exhibit reopening comes a day after prosecutors announced they would not file charges against the boy’s mother in the May 28 incident.

The exhibit has a new barrier meant to make it more difficult for members of the public to get into the habitat, zoo officials said.

The new barrier features a 42-inch tall railing with solid wood beams at the top and bottom linked by a knotted rope netting, the zoo said last week.

“Our exhibit goes above and beyond standard safety requirements, but in light of what happened, we have modified the outer public barrier to make entry even more difficult,” said Thane Maynard, director of the Cincinnati Zoo, in a statement.

Jacob and Krista Ward came to the zoo Tuesday with their three kids — ages 4, 2 and eight months — in tow.

“The zoo should have probably taken better precautions since it’s a place kids go,” Krista Ward said.

But she added that what happened at the zoo is “one of those things you never imagined could happen.”

When the Wards are out and about with three children they always have a system to keep their kids close.

“We always hold one. One holds a hand and one on the shoulder,” Krista Ward says. “And if need be, we use the leash.”

But Jacob Ward knows sometimes it isn’t that simple.

“It can happen to anyone,” he says. “All it takes is a split second for a kid to get away.”

The zoo has staunchly defended its decision to shoot Harambe as necessary to protect the child, but has faced criticism from some who argued it could have tranquilized Harambe or did too little to prevent the tragedy in the first place.

Others blamed the child’s mother for failing to supervise him adequately.

An online petition seeking charges received more than 500,000 signatures.

One witness said she overheard the boy telling his mother he was going to get into the moat.

“The little boy himself had already been talking about wanting to go in, go in, get in the water and his mother is like, ‘No you’re not, no you’re not,’ ” said Kimberley Ann Perkins O’Connor.

The mother admonished her son to behave before becoming distracted by other children with her, O’Connor said.

“Her attention was drawn away for seconds, maybe a minute, and then he was up and in before you knew it, she said.

In announcing his decision not to seek charges in the case, Hamilton County Prosecutor Joseph Deters said Monday that there was no evidence the child’s mother failed to act appropriately.

“She had three other kids with her and turned her back. … And if anyone doesn’t believe a 3-year-old can scamper off very quickly, they’ve never had kids.”

Molly McCray said that’s why she often uses a leash to make sure she doesn’t lose her children.

She walked her young daughter Mila through the zoo on the leash on Tuesday.

“I’m not ashamed of a leash. Kids take off in a split second and you never know,” McCray said. “The most diligent parent can lose track.”

Both the U.S. Department of Agriculture and the Association of Zoos and Aquariums have launched investigations into the Harambe episode.

The USDA, which inspects the zoo annually, will look into whether the facility was in compliance with a federal law that monitors the treatment of animals in research and exhibition.

The Association of Zoos and Aquariums is the group that accredits zoos.

“In the case of this incident, which involved a child and a critically endangered animal, our collective goal is to take steps to assure it doesn’t happen again,” Kris Vehrs, the interim president and CEO of the zoo association, said in a statement.

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