A Swedish zoo shot dead three chimpanzees on Thursday after they escaped their enclosure, officials said in a statement.
A press release from the Furuvik Zoo said five of its seven chimpanzees had escaped their enclosure around noon on Wednesday.
It said that for security reasons, shooters were then positioned in the park in case the animals also escaped from the larger chimpanzee house that their enclosure is a part of.
"During the day, unfortunately, three chimpanzees had to be euthanized for safety reasons," the zoo wrote.
A fourth chimpanzee was also shot and wounded but did not die. A later statement from the zoo on Thursday said the four remaining primates were all in the chimpanzee house but none was secured in its enclosure.
Tranquilizer darts too slow to take effect, require close-range shot, zoo says
Officials at the zoo explained their decision to shoot the animals after users on social media questioned them and asked why they hadn't chosen to use tranquilizers.
Authorities explained in their statement that chimpanzees can be perceived as peaceful but are dangerous.
"They are fast, very strong and generally fearless," the statement said, adding that the situation with animals on the loose could quickly "turn into a life-threatening situation."
Authorities said that using tranquilizers was not an option for them since they would be putting human lives at risk.
To shoot with tranquilizer darts, you need to be very close to the animal, the statement read. The zoo also said the darts could take up to 10 minutes to take effect and that would pose danger to human safety.
In a statement on their Facebook page, Furuvik Zoo said the animals were cared for and cherished and that the decision to shoot the animals was not taken lightly.
Other chimpanzees still outside enclosure
The zoo said on Thursday that after a "quiet" night, the four remaining chimpanzees were not in their enclosure but were thought to be within the chimpanzee house, which was under guard.
"They are in the house, but not confined in their enclosure. This means that we cannot yet allow people to move freely in the park and we are still on full alert."
It said personnel were working on getting a fix on their location and then coaxing them back to their enclosure.
"We currently do not know exactly how it happened when the chimpanzees got out, but we take the incident very seriously and will conduct a full investigation and take all necessary measures to ensure that something like this cannot happen again," Furuvik Zoo wrote.
It was not entirely clear why only three of the seven animals had been shot, or how all seven chimpanzees appeared to have ultimately left the enclosure, when the zoo said five had escaped initially on Wednesday.
The zoo is currently closed to visitors for the season, and staff members have either been evacuated or ordered into safety indoors.
The chimps' escape comes on the heels of several other high-profile evasions in Sweden.
At the end of October, a king cobra slithered out of Stockholm's open-air museum and animal park Skansen and was missing for about a week until it returned on its own.
A month later, two great grey owls escaped from the aviary at the same zoo but have since flown back.
