
The perpetrators forced the main gate to Thoiry Zoo near Paris and broke through at least two other security barriers on Monday night, without disturbing five people who live on the grounds.
The animal, a four-year-old "critically endangered" southern white male named Vince, was attacked inside an area where at least two other rhinos are kept.
"Staff left the rhino enclosure on Monday. When they returned on Tuesday, an animal had been killed and its two horns had been sawn off," a police spokesperson told AFP.
She added that the horns were "probably cut off with a chainsaw".
The rhino had been shot three times in the head.
"Only the main horn was stolen," the spokesperson said.
Investigators estimate the horn is worth roughly US$42 250.
Black market rhino horn sells for up to US$60 000/kg - more than gold or cocaine - with demand principally coming from China and Vietnam, where it is coveted as a traditional medicine.
Thoiry Zoo is equipped with video surveillance, but cameras are not installed in the area where the rhinos live.
"This was carried out despite the presence of five members of staff who live on the site and [despite] security cameras," the zoo said.
The two other rhinos in the enclosure with Vince which were unharmed were a 37-year-old female, Gracie, and a five-year-old male, Bruno.
NAMPA/AFP