A 37 y.o. National Park Service wildlife biologist was found dead in his residence at the South Rim of the Grand Canyon on November 2, 2007.

The wildlife biologist had worked in Grand Canyon National Park for about two years and was involved in the park's cougar (mountain lion) collaring program (photo). Three days before being discovered dead in his residence he had presented to the Grand Canyon Clinic at the South Rim complaining of non-specific "flu-like" symptoms. He remained on sick leave from work the subsequent two days before being discovered dead in his residence.

Three days before presenting to the Grand Canyon Clinic the naturalist had skinned and performed a necropsy on a dead mountain lion.

Preliminary autopsy findings on the dead naturalist showed evidence of pneumonia.

What was the cause of the naturalist's death? Submit your answer below.