United Kingdom, Sept. 17 -- Mark Ruffalo has hailed Robert Redford as a "real American hero".

The Hollywood icon passed away on Tuesday (16.09.25), aged 89, and Mark has taken to social media to share a letter than he wrote, but never actually sent, to the late movie star.

Mark - who worked with the acclaimed actor on the 2001 movie The Last Castle - captioned his Instagram post: "This was a letter I had written to Robert Redford when I learned he was ill. I didn't get it to him before the news today. This is what a real American Hero looks like. A man who brought people together, lived and practiced empathy, and created good and useful organizations that made peoples lives better and included anyone who had an interest. Please remember...