One or more poachers sneaked into a zoo near Paris on Monday night and killed a 4-year-old male rhinoceros. Their goal was his horns.

The rhino, named Vince, was shot dead at Thoiry Zoo before the poachers sawed off one of those horns , according to CNN . It may be the first time that a living animal in captivity in Europe has been killed by poachers, The Independent wrote.

In a Facebook post , zoo officials said their entire staff is shocked.

Vince was one of only about 20,000 white rhinos in the world. Two other rhinos in the enclosure 5-year-old Bruno and 37-year-old Grace were unharmed.

[Vinces] second horn was partially cut, which left the impression that the criminals were disturbed or that their equipment was defective, the Facebook statement said.

The rhino was shot three times in the head. Investigators are working to find out what kind of gun was used.

In 2015, one kilogram of rhino horns, which are sought for their supposed medicinal properties, was sold on the black market for 51,000 euros, CNN noted. Thats a little more than $53,000.