John Unger announced Schoep's death Friday on the "John and Schoep" Facebook page, WCCO-TV , Minneapolis, reported. Schoep was 20.
"I breathe but I can't catch my breath," Unger said. "Schoep passed yesterday, more information in the days ahead."
Schoep, a shepherd mix, became famous largely because of Unger's efforts to ease the problems of old age in his pet. The photo that went viral showed Unger holding the dog in his arms as he floated in the lake, therapy for joint pain and arthritis.
Schoep had also lost his sight due to cataracts.
Unger received more than $10,000 in donations. He used the money for laser therapy to stimulate old cells, a measure that provided more relief for joint pain and probably added a year to Schoep's life, the report said.