Deeply disturbing events are happening at Dallas Zoo in Texas - with three 'suspicious' incidents happening in less than two weeks.
The worrying situation has got so bad that the Dallas Police Department has been asked to investigate the string of peculiar events.
It all began with a clouded leopard escaping its enclosure, leading to an extensive search while the entire zoo went into lockdown.
Authorities would later reveal that the leopard's enclosure had been intentionally cut open - and found similar incisions in a monkey habitat the following.
Now things have taken an even darker turn as an endangered vulture has been found dead under "unusual" circumstances.
'Covid ruined Christmas - if are not utterly selfish please wear a mask'In the past 10 days, the zoo has "substantially" increased security measures, including limiting access to outdoor enclosures and adding cameras and overnight guards.
Here is a break down of the troubling incidents that have been happening recently - and other events at the zoo which hit the headlines.
Suspicious vulture death
The most recent incident is the most disturbing, the death of an endangered vulture which has been deemed "suspicious" by officials.
The vulture named Pin, one of only 6,500 left on the planet, was found dead in its enclosure in the Wilds of Africa habitat on Sunday.
In a statement on their Facebook page, the zoo said: "This weekend, our staff found that one of the endangered vultures in our Wilds of Africa habitats had died. The animal care team is heartbroken over this tremendous loss. Please keep them in your thoughts as they process what has happened.
"The circumstances of the death are unusual, and the death does not appear to be from natural causes. Given the recent incidents at the Zoo, we alerted the Dallas Police Department. We cannot share many details until Dallas PD has had more time to look into this matter.
"In the past week, we have added additional cameras throughout the Zoo and increased onsite security patrols during the overnight hours. We will continue to implement and expand our safety and security measures to whatever level necessary to keep our animals and staff safe."
Dallas police say they are investigating the male lappet-faced vulture's death and a necropsy will be conducted on its body.
At a Monday press conference, Dallas Zoo CEO Gregg Hudson said that the vulture was found wounded but declined to comment when asked whether the bird was shot.
"We're going to continue to expand and implement whatever it takes for the safety and security measures of the animals, the staff and the people that live near the zoo," Hudson said.
Police in hunt for suspected tiger on loose in countryside after big cat spottedMayor Pro Tem of Dallas, Carolyn King Arnold, said officials are not only trying to protect those inside the zoo, but those in surrounding neighbourhoods.
Leopard escape
The first worrying incident happened just over a week ago, when a clouded leopard escaped its enclosure.
Three-year-old Nova fled her pen and was eventually found nearby after several hours of frantic searching.
The zoo announced a "serious situation" and went into lockdown with a "code blue", indicating a non-dangerous animals was on the loose.
The 25-pound big cat, who did not pose a risk to humans, was reunited with her sister, who had stayed in their enclosure.
In a statement on Twitter, the zoo said: "We are thrilled to report we located clouded leopard Nova on-grounds at the Zoo this afternoon at approximated 4:40 p.m.
"She was located very near the original habitat, and teams were able to safely secure her just before 5:15 p.m."
However, it was discovered that the leopard had escaped because someone had intentionally cut the fence.
Monkey enclosure cut
There was more than one suspected sabotage at the zoo, as officials revealed another incision had been found in an enclosure which houses langur monkeys.
None of the animals escaped and none of them were harmed or appeared to be in danger, the police department said.
A criminal mischief report was filed and investigators began working to determine whether the two incidents were linked.
Gorilla rampage
Back in March 2004, a massive 300-pound gorilla went on a 40-minute rampage after escaping from his enclosure.
Jabari scaled a wall after some youths had reportedly been teasing the 13-year-old male western lowland gorilla.
Police evacuated an estimated 300 people from the zoo and four people were left with injuries, including a three-year-old who was in the gorilla's mouth.
"I was like, 'This is not happening, this is so unreal,' cause he just came out of nowhere," mum Keisha Heard said on NBC's Today show.
"I'm watching this gorilla. He has my son in his mouth, he's attacking him, and I tried to help him and there wasn’t really anything that I could do. ... He slings me back across the concrete area where we are. So it was really scary."
Zoo workers armed with tranquilizer guns had pursued Jabari through the forested jungles of the Wilds of Africa exhibit for about 40 minutes.
But could not gain a clear shot, officials said, and then shot the gorilla dead when he charged at officers.
"It tried to charge two of our officers, so we had to shoot it," Deputy Police Chief Daniel Garcia said.
"You can imagine the pandemonium we had out here when he got loose. We felt terrible we had to put this animal down."
Lion kills lioness
Visitors were horrified in November 2013 when a lion attacked and killed a lioness.
The male big cat inflicted terrible injuries after it grabbed five-year-old Johari by the neck - with a post-mortem examination finding the female died from neck wounds and haemorrhaging.
Johari, known as Jo-Jo, was a staff favourite who was "sweet and loving with her sisters, and often could be found grooming them".
Officials said the captive-born lions had lived together peacefully for years - and males attacking females is extremely rare.
Witness Jim Harvey told local news station WFAA: "Everyone thought they were playing at first but then they could see that she was struggling."
Lynn Kramer, the then vice-president of animal operations and welfare at the zoo, said in a statement: "Johari was a remarkable animal, as are all of our lions.
"This is a very rare and unfortunate occurrence. In my 35 years as a veterinarian in zoos, I've never seen this happen."
Giraffe beaks neck
In July 2015, a baby giraffe died after running into the edge of her enclosure and breaking her neck.
The calf, called Kipenzi, became a global star after she was born on live television and thousands queued when she made her first public appearance.
Sadly, Kipenzi, described as one of the friendliest and most charismatic of the zoo's large herd, was running in the feeding yard at Dallas Zoo when she made a sharp turn and hit the fence.
She broke three vertebrae in her neck - and staff said the three month-old died immediately.
"This is a huge loss for our giraffe herd, our staff and our guests," said Gregg Hudson, then president and CEO of the Dallas Zoo.
"To be honest, it hurts terribly. We’re crushed, and everyone here is mourning. Please keep our staff in your thoughts."