A black rhinoceros that made the Denver Zoo its home died Wednesday after being euthanized following persisting foot problems, zoo officials said.

The rhinoceros, known as Mshindi, was 21 years old and his chronic foot problems got progressively worse over the last 1 1/2 years, forcing zoo staff to end his pain and euthanize him, according to CBS.

"The median life expectancy for black rhinoceroses living in North American zoos is 17.8 years," the zoo said in a statement.

"This is very hard for all of our staff. We'll miss him terribly, but we knew this was the right thing to do," Curator of Toyota Elephant Passage Dale Leeds said. "Mshindi was well-known and loved by our zookeepers and guests for his wonderful personality."

The zoo explored many treatment options and became optimistic in June when Mshindi responded and showed improvement in June. However, he soon stopped responding, and his condition began to worsen, according to MarketWatch.

"We watched Mshindi very closely and were optimistic about his recovery, but he was no longer responding to his treatment," Vice President of Veterinary Medicine Scott Larsen said.

Mshindi was born at the Denver zoo in 1993 to parents Lij and Rhinestone and was given his name, which means "warrior" or "champion" in Swahili, reported The Denver Post. The rhino became well known for his artistic talents after he learned to hold a brush in his mouth and paint on a canvas held by a zoo staff member. His art was sold, and the proceeds were used to raise money for a rhino conservation.

"He will be missed dearly," Larsen concluded.