SCOTTSBLUFF, Neb. -- A five-year-old grizzly bear at the Riverside Discovery Center has died, zookeepers announced Thursday.

The grizzly bear, Bandit, had been at the facility since he was approximately 10 months old. He had arrived with his brother, Smokey, when their mother was illegally killed and both brothers were left orphaned.

"It's not very often you meet an animal that seems like they can see into your soul, but Bandit was that animal for me," Zookeeper Sierra Spears said. "Bandit was always excited for our daily training sessions and that made me even more excited to work with him. He made me rethink the way I communicated with animals through training and we would work through the barriers of learning something new every session."

The animal care staff noticed a loss of appetite and immediately notified the zoo veterinarian. Medical therapy was initiated the same day. Within 24 hours, Bandit's condition deteriorated and he was transported to Colorado State University's Veterinary Teaching Hospital for further testing.

Upon returning to the RDC, Bandit received supportive care and numerous treatments aimed at his symptoms. Despite the efforts of on-site staff and medical experts, Bandit succumbed to his illness after a week of treatments.

A necropsy was performed by the zoo's veterinarian and sample testing was conducted by the Nebraska Veterinary Diagnostic Center at UNL. It was determined that he had encephalitis. At this time, the cause of the encephalitis is undetermined. RDC is still awaiting further test results. The initial necropsy also showed that Bandit had a genetic heart condition called dilated cardiomyopathy.

It is unknown whether this contributed to his illness or was an incidental finding.

"This is an incredibly tough loss for all of the staff at RDC and for the entire community," RDC Executive Director Anthony Mason said. "Bandit was an incredible animal with a larger than life impact on everyone. I want to applaud our staff who worked around the clock for over a week to provide care and treatment for Bandit. I can't possibly overstate the herculean effort put forth by veterinarians, keepers, maintenance staff, and many others. His turn for the worse was unexpected but I want to assure the community that we did everything we could for him. Every member of our team is heartbroken at his loss. His brother, Smokey, is doing just fine and not showing any indications of any type of illness. Animal care staff are closely monitoring him and providing him with lots of extra enrichment."