Frankfurt Zoo officials announced on Tuesday that they'd identified the fugitive responsible for killing 15 flamingos living in the German animal facility.

Tests performed during the investigation showed the killer was a fox, the Associated Press reported.

According to Manfred Niekisch, director of operations at the zoo, most members of staff were relieved to find out that the flamingos, some of whom were beheaded, were not killed by a human.

Officials initially feared the worst, after they discovered nine long-necked Chilean birds dead on Friday morning. The New York Daily News reported zoo keepers opened the flamingo enclosure to find the animals - each worth nearly $1,400 - slain in their quarters overnight.

Police kept watch for the evening, but the killer managed to strike again. Officials reportedly found an additional six flamingos the following morning that appeared to have been stabbed to death. Others had bite marks on their bodies, which suggested a fox had attacked the birds.

Investigators originally wagered a fox might have bitten the flamingos after they'd already died.

Niekisch told The Local over the weekend that law enforcement officials performed necropsies and heightened surveillance around the facility.

Zoo employees have planned to switch security measures for the birds - Niekisch told the Associated Press that the birds will be locked away at night. Live fox traps and an electric fence will be constructed as well, in efforts to protect the rare flamingos.