Update - 3pm: A woman claiming to be the mother of the boy who fell into a gorilla enclosure in Cincinnati Zoo, leading to the animal's shooting has said that "accidents happen".
Michelle Gregg, broke her silence saying people were too quick to judge parents.
She wrote on Facebook: “I want to thank everyone for their thoughts and prayers today. What started off as a wonderful day turned into a scary one.
“For those of you that have seen the news or been on social media that was my son that fell in the gorilla exhibit at the zoo. God protected my child until the authorities were able to get to him.”
“My son is safe and was able to walk away with a concussion and a few scrapes ... no broken bones or internal injuries.
“As a society we are quick to judge how a parent could take their eyes off of their child and if anyone knows me I keep a tight watch on my kids. Accidents happen but I am thankful that the right people were in the right place today.”
Earlier: The director of the Cincinnati Zoo says it remains safe for its 1.6 million annual visitors despite a weekend tragedy in which a gorilla was fatally shot to protect a four-year-old boy who had entered its exhibit.
Thane Maynard, however, said a review is under way to determine any improvements that can make the zoo safer.
The male western lowland gorilla named Harambe was killed on Saturday by a special zoo response team that feared for the boy's safety. Video taken by zoo visitors showed the gorilla at times appeared to be protective of the boy but also violently dragged him through the shallow moat.
Mr Maynard said the decision to kill the gorilla was the right one. He said the gorilla was agitated and disoriented by the commotion during the 10 minutes after the boy fell. He said the gorilla could crush a coconut in one hand and there was no doubt that the boy's life was in danger.
In an interview with Boston television station WFXT, conservationist and television host Jeff Corwin suggested that the boy's family should shoulder some of the blame, saying "zoos aren't your baby sitter".
"I don't think this happened in seconds or minutes. I think this took time for this kid, this little boy, to find himself in that situation. Ultimately it's the gorilla that's paid this price," he said.
A Cincinnati police spokesman said no charges against the parents were being considered. A spokeswoman for the family said they had no plans to comment.
"I do think there's a degree of responsibility they have to be held to," said Kate Villanueva, a mother of two children from Erlanger, Kentucky, who started the Justice for Harambe page and attended a vigil for the gorilla outside the Cincinnati Zoo on Monday. "You have to be watching your children at all times."
The Gladys Porter Zoo in Brownsville, Texas, where Harambe spent most of his life, said its staff is deeply saddened by the gorilla's death. Harambe was sent to Cincinnati less than two years ago in hopes he would eventually breed with gorillas there.
Jerry Stones, facilities director at Gladys Porter Zoo raised Harambe since birth and has worked with the gorilla's family since they first entered the US, the Brownsville Herald reported.
Mr Stones said: "He was a character. He grew up to be a beautiful, beautiful animal, never aggressive and never mean. He would tease the heck out of people and would do things to irritate you just like some kids."
Mr Stones said he would take Harambe home with him when the gorilla was a baby and let him sleep on his bed, according to Texas television station KRGV-TV.
There are critics of the zoo's decision to kill Harambe. The People for the Ethical Treatment of Animals said the zoo should have had better barriers between humans and the gorillas.
Mr Maynard said the atmosphere following the incident is "very emotional".
"Not everyone shares the same opinion and that's okay," he said. "But we all share the love for animals."
Mr Maynard said the zoo has received messages of support and condolences from around the world, including from other zoo directors and gorilla experts.
He said zoo visitors have been leaving flowers at the exhibit and asking how they could support gorilla conservation.