No, it was not his last painting. You’re correct about Van Gogh’s purported reason for taking the gun with him–he had complained that the crows were bugging him, and he told Dr. Gachet that he needed a gun to scare them away. I can’t remember if it was a revolver–for some reason, I think it may have been a rifle.
The Crows over the Wheatfield is often said to be the painting he was working on when he shot himself, but that’s mainly because with its dark, foreboding sky, and the meandering path lost amidst the fields, it looks like the perfect suicide note for an artist. Also, I think the film Lust for Life (featuring Kirk Douglas as Vincent) had him working on it at the end, and that’s kind of reinforced the “suicide note” impression of the painting. The funny thing is that Vincent painted some much warmer, “happier” paintings after the Crows–though which work was exactly his last is probably still debateable.
The soft-documentary I was watching just last night (Van Gogh Gauguin) showed him writing a letter to Theo, stopping mid-paragraph, and going out to the field to paint but not actually doing any painting & just offing himself right away.
So Theo died that year too? I missed that part of the story.