Complex sentence: He talked with Mark Vasina of Nebraskans for Peace, who had collaborated with the tribe in protests and was filming a documentary about the issues, which was released in 2008 as "The Battle for Whiteclay".
Split into simpler sentences: He talked with Mark Vasina of Nebraskans for Peace, who had collaborated with the tribe in protests. Vasina's documentary about the issues and activism was released in 2008 as "The Battle for Whiteclay".