Timothy Treadwell was many things: infinitely charismatic, infectiously enthusiastic, childish, foolish, delusional and probably manic-depressive. He was also doomed, something we know before walking into “Grizzly Man,” Werner Herzog’s extraordinary new documentary.

That doesn’t necessarily make Treadwell’s story more tragic; by living among the bears in the Alaskan wild for a dozen years and treating them as if they were friends, it would seem his October 2003 mauling was inevitable. (His girlfriend, Amie Huguenard, also died in the attack; their remains were found near their campsite.)

But it does make Treadwell’s tale morbidly compelling, and provides a natural jumping-off point for a number of larger issues regarding nature, civilization, spirituality, love and even filmmaking itself.

Herzog, the veteran German director (“Aguirre, The Wrath of God,” “Nosferatu the Vampyre”) who has turned increasingly to documentaries in recent years, skillfully weaves all of this together and even finds time to comment on Treadwell’s own skills as a filmmaker.

During his last five summers in Alaska’s Katmai National Park and Reserve, Treadwell shot some 100 hours of footage, from the shocking (two grizzlies violently grappling over a female, “the Michelle Pfeiffer of bears,” he calls her) to the sublime (a baby fox running spiritedly through tall grass). Purely as a nature film, “Grizzly Man” would have been spectacular, full of sprawling fields, rushing waters and endless skies.

Timothy Treadwell lived among the bears in the Alaskan wild for a dozen years before being killed by one in 2003. His story is the impetus for Grizzly

Treadwell, in placing himself in the frame for much of the action, proves he would have been the quintessential reality TV star if he hadn’t already retreated to the wild before the advent of “Survivor.” His amped-up surfer-dude act is funny, engaging and seems totally spontaneous.

Outtakes, however, reveal that he was obsessively methodical about what he shot and how he shot it, even down to the color bandanna he was wearing on his head during stand-ups.

The 46-year-old coos at these enormous creatures as they roam just a few feet away, tells them he loves them and gives them cuddly names like Mr. Chocolate and Aunt Melissa. He also describes himself as a “kind warrior” and vows that he would die for these animals, “but I will not die by their claws and paws.” (The irony is, that’s exactly what happened to him, and we know that from the start.)

Herzog lets us fall in love with him – certainly this is a brave, interesting man doing brave, interesting work – before slowly, tantalizingly revealing his dark side. Treadwell completely fabricated his back story, telling people he was from a small town in the Australian outback (and doing a lousy fake accent that sounded Kennedyesque, one friend recalls) when in reality he grew up on New York’s suburban Long Island. He received a scholarship to swim in college, then injured his back, dropped out and moved to Los Angeles to become an actor. (Treadwell is his stage name.)

His father recounts how Treadwell auditioned for the role of Woody on “Cheers,” and supposedly came in second to Woody Harrelson. After failing to get the part, “He spiraled down,” dad says. Drug abuse and alcoholism followed. But Treadwell says his first encounter with the bears during a trip to Alaska in 1989 saved him. They inspired him to get sober and gave him a purpose in life: to be their protector.

Interviews with friends, colleagues and critics offer a balanced look at this complicated man. His champions (including ex-girlfriend Jewel Palovak, the film’s co-executive producer) posthumously deify him for his sacrifices, his personality and his heart. Native Alaskans who weren’t so pleased with his work say he got what was coming to him for violating the long-respected boundaries of nature.

Some of the most riveting testimony comes from Frank G. Fallico, the medical examiner who describes what happened to Treadwell and Huguenard in wide-eyed, detailed fashion. (He’s such a natural storyteller, so seemingly odd but clearly kindhearted, he’s worthy of a documentary of his own.)

Herzog slips a bit into self-indulgence by including footage of himself being visibly moved by the audio recording of the fatal mauling (the lens cap was on so there’s no video) and urging Palovak to destroy the tape. He also offers voiceover opinions about Treadwell, his work and about the bears themselves.

The grizzly man and “Grizzly Man” don’t need the help. Both prove they can stand just fine on their own until the very end.