For more than a century, art historians have agreed that a depressed Vincent van Gogh killed himself. But in a new biography, Van Gogh: The Life, Pulitzer-Prize winning authors Steven Naifeh and Gregory White Smith argue that the Dutch impressionist painter might have been murdered. Here's what you need to know about their theory:

Why do people believe Van Gogh killed himself?
He said so. The accepted story of the troubled artist's death is that he walked into a wheat field to paint, but ended up shooting himself in the chest with a pistol. He then dragged himself more than a mile back to the room he was renting in a boarding house in the French town of Auvers-sur-Oise, northwest of Paris. He told his brother Theo, his doctors, and the police that he had shot himself. "Do not accuse anyone," he said. "It is I who wanted to kill myself".

What made these authors suspect murder?
The accepted version of events just "didn't make sense," co-author Smith said Sunday on 60 Minutes. Yeah, "how did he climb through these vast wheat fields and down the escarpment into the town?" Naifeh asked. "It's extremely difficult to imagine that in that physical condition he could have made that trip." Plus, the gun was never found, nor were Van Gogh's painting materials. The bullet also hit Van Gogh at "a crazy angle," the authors say, and appeared to have been fired from too far from the body for Van Gogh to have fired it himself. Naifeh and White also argue that Van Gogh's suicide confession seemed oddly hedged, as if he were trying to protect someone.

So who dunnit?
The authors think Van Gogh was shot by a friend's 16-year-old brother. The boy, Rene Secretan, liked wearing cowboy outfits, complete with a revolver on the hip. Decades after Van Gogh's death, Secretan, by then a wealthy businessman, gave an interview confessing that he and his friend had teased the lonely artist mercilessly. The authors, citing an art historian who heard rumors in the 1930s that Van Gogh had been shot accidentally by two boys, theorize that Secretan and a friend shot Van Gogh — perhaps the hot-tempered artist lunged at him while being taunted, or maybe it was just a cowboy game gone awry. Then, the theory goes, Van Gogh, who had complained he was tired of living, protected the boys because he figured they had done him a favor.

Is everyone buying this?
Nope. The curator of the Van Gogh Museum in the Netherlands complimented the book, but said historians "cannot yet agree" with the murder theory.

Sources: ABC News, BBC News, Global Post, NY Times