Rosewood (1997)
In 1923, a racist lynch mob attacks an African American community in Rosewood, Florida. Among the carnage, a music teacher Sylvester (Don Cheadle) and a mysterious stranger (Ving Rhames) stand against the invaders, while a grocer (Jon Voight) attempts to save the town’s women and children.
loser guy wants to shoot up his office but becomes a hero against his will
yeha, that's fiction