A rare female Sumatran tiger has been killed by her intended mate, Toronto Zoo officials said Thursday.

Brytne, a 13-year-old female tiger and Harimau Kayu, a three-year-old male tiger, seemed "hunky dory" when keepers checked on them Thursday morning, Maria Franke, Curator of Mammals, told CTV News.

Around 9 a.m., however, "one tiger did something that the other tiger didn't like" and a fight ensued, said Franke.

Before the pair could be separated, Brytne suffered a serious neck injury. Franke said staff were quick to intervene but the tiger died of a crushed larynx.

"The keepers did an awesome job separating them right away -- but it only takes seconds" for tigers to inflict mortal wounds, continued Franke.

Harimau Kayu came to the Toronto Zoo from the San Diego Wild Animal Park. When he was introduced to Brytne in June, it was hoped the pair would breed.

Brytne had already given birth to two litters with another male tiger, Rengat. Their cubs were the first Sumatran tigers born in Canada. Rengat was later put down after suffering from kidney failure.

Zoo staff stress that tigers rarely fight each other, in captivity or the wild.

In a statement, the zoo said its staff is "devastated by the loss of this beautiful and loved animal of the Zoo community."

Sumatran tigers are a critically endangered species, with an estimated 300 to 500 in the wild, according to the International Union for Conservation of Nature (IUCN). They're based on the Indonesian island of Sumatra.