A group of chimpanzees escaped from their enclosure at Belfast Zoo on Saturday afternoon after making an improvised ladder from tree branches.
One chimpanzee jumped out of the enclosure and walked along a path with members of the public, while others sat on a wall above the enclosure and watched.
Dean McFaul and Danielle Monaghan filmed the escape attempt and circulated the videos on social media where they went viral.
They were at the zoo with Ms Monaghan's children Grace (8) and Leo (6), and Mr McFaul's four-year-old nieces Summer and Willow.
The couple, who live in Holywood were amazed at what they saw.
Mr McFaul said that there was no doubt in his mind that the escape was "orchestrated" and that the chimpanzees worked as a team to escape the enclosure.
"They started walking out of the hut one by one, it was like they organised what they were going to do," he said.
"They grabbed a plank of wood, walked to the other side of the enclosure, put the wood against the wall and then they all lined up and started climbing up the wall.
"There were none in the enclosure and we were about to walk away when they appeared from the hut. It was crazy."
He said that he was not overly concerned because the chimpanzees did not appear aggressive.
"We kept the children back, but there was no noise from the chimpanzees, no aggression," Mr McFaul said.
"We were so shocked we didn't know what to do, one of them grabbed a branch and jumped back up and started eating it.
"Another jumped down and started walking towards us, we walked right by it. It was sitting right beside my foot."
Mr McFaul said that zoo staff were concerned when they learned about the escape.
"They were shocked and they told us to 'get the kids and get out right now'," he said.
"It seemed like they thought they might do something".
Mr McFaul said that the experience didn't ruin their trip to the Zoo and said it had been the "best day ever".
Belfast Zoo spokesperson Alan Cairns said that the chimpanzees had been able to build the ladder after the trees in their enclosure had been weakened by storms.
He said they only remained outside their enclosure for a short time before returning as they were "quite cowardly".
"They're intelligent primates and know they're not supposed to be out of their enclosure, so got back in themselves," Mr Cairns told the BBC.
"We like things to be natural in their enclosure, to have trees in it, but we will review it.
"We may have to remove the trees or make them a smaller level, although we don't want to do that."
He confirmed that the chimpanzees were then locked in their enclosure to prevent a further breakout.
A Belfast City Council spokesperson said that one chimpanzee left the enclosure before quickly returning.
"Belfast Zoo would like to thank members of the public who helped raise the alarm as zookeepers moved in to return the animal to its enclosure," the spokesperson said.
Alliance councillor Nuala McAllister said she would be asking council for an urgent review into safety measures at Belfast Zoo.
The latest escape attempt comes after a red panda escaped from the zoo last month.
Endangered Himalayan native cub Amber made her escape after two electricity fences failed at the zoo.
She was eventually found safe and well in Collinbridge, a residential area within a mile of the zoo's grounds.