Kamau, the Dallas Zoo’s beloved 6-month-old cheetah cub, died Tuesday afternoon from pneumonia.

Kamau and his brother, Winspear, became sick last week and were treated around the clock by veterinary staff, the zoo reports.

Winspear is recovering and in stable condition. Kamau, who was smaller, became gravely ill Tuesday. Zoo staff tried to resuscitate him.

Kamau, pronounced ka-MOWH, died at 2:15 p.m.

A necropsy indicated evidence of pneumonia.

Kamau and Winspear were buds. Kamau loved to pounce on top of his brother.

“These types of illnesses can worsen very quickly in both animals and people,” Lynn Kramer, the zoo’s vice president of animal operations and welfare, said in a news release.

Both Kamau and Winspear were vaccinated against canine and feline distemper and other respiratory illnesses, the zoo reports. Other cats at the zoo are healthy.

The cubs have a companion, a black Labrador puppy named Amani – he is not ill, zoo officials say.

The cubs were born July 8 and became fast friends with zoo visitors.

Here’s a Dallas Zoo video of the cubs: