The ‘Back to the Future’ Michael J. Fox announced the news of the death of his dog on his social media handles on Monday. While sharing a photo of the 12-year-old pooch on his Instagram, he wrote, "Gus — great dog and loyal friend, we'll miss you.”

In addition to his tribute, Fox also posted numerous photos of himself with Gus throughout the years on his Instagram Stories.

Gus had been a devoted companion for Fox in his ongoing battle with Parkinson's disease. In his book, Fox called the Great Dane-Labrador mix a "wonder dog" for being a constant source of support throughout his health struggles, reports people.com.

"I didn't rescue Gus," the actor wrote. "You can argue that he rescued me, but he'd be too modest to make that claim."