A wild fox got into an outdoor bird habitat at the Smithsonian National Zoo in Washington, D.C., killing 25 flamingos and injuring three.

Zoo staff entered the habitat Monday to find the deceased birds. They also saw the fox scurry away when they arrived. The flock originated with 74 flamingos. A pintail duck was also killed by the fox, according to a press release Tuesday from the zoo.

"This is a heartbreaking loss for us and everyone who cares about our animals," Brandie Smith, director of the Smithsonian's National Zoo and Conservation Biology Institute, said in the release.

"The barrier we used passed inspection and is used by other accredited zoos across the country. Our focus now is on the well-being of the remaining flock and fortifying our habitats."

The zoo said that the last inspection done to the bird habitat was Sunday around 2:30 p.m. ET, and that there were no areas of concern at that time. It will be investigating the incident and how the breach was possible.

Smith explained in an interview that the fox must have been "very determined" to most likely feed its young.

“I can’t even imagine the effort," Smith said, according to the New York Times.

Following the incident, the zoo said it reinforced the metal mesh for the flamingo yard, added traps around the outdoor yard to catch predators, and digital camera traps with an infrared sensor to see overnight activity.

The remaining flamingos were moved indoors and the ducks were moved to a covered, secure outdoor space.

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