"Dark Blood" was not an easy production. The material was heavy, they filmed in desolate locations and Davis was difficult to work with and was often hard on Phoenix. He also had dyslexia and struggled to remember long segments of dialogue, which he occasionally asked Sluizer to shorten.
But Sluizer marveled at Phoenix's ability to embody a character with such depth.
"It's what comes out of him and the charisma he has plus the fact that he knows how to express a character when he has got hold of it," Sluizer said.
Pryce, who said he was a fan of Phoenix's work in "Stand By Me," often met the young actor and his friends for dinner, finding camaraderie in the isolated Utah desert.
"You do become incredibly close when you work together in a film ... I felt enormous empathy with him. I liked him very much," Pryce said.
The two insist Phoenix was not using drugs while filming in Utah. But something was noticeably wrong with Phoenix when the crew returned for a shoot in Los Angeles. His eyes floated, he walked differently and sat listlessly for long periods of time.
"He had been taking something. That was quite visible," Sluizer said.
The next morning the cast and crew received the news.
"It was a complete shock and to be woken at 5 o'clock in the morning and the first thing that somebody says to you is, 'River's dead,'" Pryce said.
"It left us totally sad and after River's death. I nearly said I don't want to make movies anymore," Sluizer lamented.
He dismisses any notion that the film is exploiting River's death.
Sluizer said he spoke with Phoenix's mother, Arlynn "Heart" Phoenix, and invited her and other family members to attend the Berlin premiere last month where the film received a standing ovation.
"She said, 'Well, good luck with the movie but we are not participating'," saying the family felt the movie was finished, Sluizer said.
R.E.M. frontman Michael Stipe, who stayed with Phoenix for a few days while he was filming in Utah, also attended the Berlin premiere.
"It's a piece of work that belongs not just to River but all of us in the film and it was right that (Sluizer) completed it in the way that he did," Pryce said.
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