Police may bring criminal charges over a Cincinnati Zoo incident in which a gorilla was killed to rescue a four-year-old boy who had fallen into its enclosure, a prosecutor said.
The death of Harambe also prompted the animal rights group Stop Animal Exploitation Now to file a negligence complaint against the zoo with the US Department of Agriculture.
The group is seeking the maximum penalty of $10,000 (€8,983).
The group said in its complaint letter that the child's ability to get past the barrier was proof the zoo was negligent and should be fined for a "clear and fatal violation of the Animal Welfare Act."
Growing outrage over Saturday's killing of the Western lowland silverback, an endangered species, sparked criticism of both the zoo and the child's parents.
Online petitions atchange.org drew more than 500,000 signatures demanding "Justice for Harambe."
Cincinnati police are taking a second look at possible criminal charges in the incident after initially saying no one was charged.
There was no indication of whether the investigation would focus on the zoo or the child's parents.
"Once their investigation is concluded, they will confer with our office on possible criminal charges," Hamilton County Prosecutor Joseph Deters said in a statement.
Witnesses said the child had expressed a desire to get into the enclosure and climbed over a 1 metre barrier, falling 4.6m into a moat.
Zookeepers shot the 17-year-old gorilla after he violently dragged and tossed the child, officials said.
The boy's mother said on Facebook that the boy suffered a concussion and scrapes but was otherwise fine.
Thane Maynard, director of the Cincinnati Zoo & Botanical Gardens, yesterday stood by the decision to shoot Harambe, saying he was not simply endangering the child but actually hurting him.
The animal had dragged the boy through shallow water and up a rock wall on Saturday, but he did not appear to intentionally harm the child.
"We are heartbroken about losing Harambe, but a child's life was in danger and a quick decision had to be made," Mr Maynard had said in a statement on Sunday.
Tranquilisers were not an option because they could have a delayed effect and "the impact from the dart could agitate the animal and cause the situation to get much worse," he said.
Looking at the incident through Harambe's eyes, his former caretaker, Jerry Stones, said in a CNN interview that the breach of his habitat was likely confusing.
"Here is this animal that has this strange thing in his house," Mr Stones said on CNN. "He knew what adult people were but he'd never been around children. It smells similar, it looks similar but 'What is it? Do I play with it? Am I supposed to be afraid of it? What do I do?'"
Even Republican presidential candidate Donald Trump jumped into the fray at a news conference, saying, "The way he held that child, it was almost like a mother holding a baby ... It was so beautiful to watch that powerful, almost 500-pound gorilla, the way he dealt with that little boy.
"But it just takes one second ... one little flick of his finger."
