A marksman has shot dead a chimpanzee which escaped from its zoo enclosure.
The animal - described as an adult female and potentially dangerous - got free at Flamingo Land near Malton, North Yorkshire.
A zoo spokesman said a probe was under way into how the animal came to escape and had to be shot.
They killed it when it became aggressive after being tranquillised, the zoo said. Animal rights activists are demanding a public investigation.
The zoo is home to more than 1,000 animals, including Siberian Tigers, zebras, camels, monkeys and meerkats.
In a statement, the zoo said: "The animal became extremely aggressive after having been tranquillised, resulting in a potentially dangerous situation for the personnel in attendance.
"As a consequence, the animal had to be destroyed at the scene.
"All the appropriate authorities have been informed and a full assessment is under way. No members of the public were in any danger as a result of this incident."
Animal rights campaigners have expressed concern over the incident.
The Captive Animals' Protection Society told BBC News: "The council must carry out an immediate public investigation into this incident to assess how this happened and to ensure the safety of animals in the zoo as well as visitors and staff.
"The zoo has been at the centre of controversy in recent months after council investigations into complaints concerning animal welfare resulted in the zoo banning three councillors from the zoo."