YOUNTVILLE, Calif. — Perhaps it began with the red Adidas gym bag stuffed with $800,000 in cash.

Then came the trail of overhyped and failed wine ventures here in the heart of Napa Valley, and the furious court battles between Robert Dahl, who ran a struggling vineyard, and his chief investor, Emad Tawfilis, who had willingly handed over the gym bag to offer the vintner seed capital.

Their dispute, in a region where money flows like, well, wine, climaxed Monday in the style of a pulp fiction thriller, with a wounded Mr. Tawfilis racing frantically through the grapevines as Mr. Dahl, carrying a silencer-equipped .22-caliber semiautomatic pistol and driving a black sport utility vehicle, methodically pursued and then killed him in sight of arriving sheriff’s deputies.

Mr. Dahl, 47, a former Minnesotan with a checkered background, later shot himself to death as officers closed in after a chase up a twisting valley road.