(CNN) -- New video captured hours before Michael Brown was killed shows the 18-year-old exchanging marijuana for cigarillos with the clerks of a Ferguson, Missouri, store, a documentary director told CNN on Monday.

Director Jason Pollock, whose film "Stranger Fruit" debuted at the South by Southwest festival in Austin over the weekend, said the video shows that Brown did not rob the store before being stopped by police and that surveillance footage purporting to show Brown engaged in a robbery at the Ferguson Market and Liquor stores was actually video of Brown returning to the store to retrieve the cigarillos the clerks gave him.

"This is a shady store. We've asked a lot of people in this community. You can buy weed at the store," Pollock said.

Pollock suggests that had this footage been released, it would've altered the notion that Brown was shot after robbing the store. He learned of the footage from a St. Louis County police report that mentioned a video from 1:13 a.m. the day of Brown's death.

In an earlier interview, in which he appeared alongside Brown's father, Pollock said, "What this video shows is that (police) lied to the world about what happened. They wanted to make Mike look bad, so they put out half a video to destroy his character in his death."

Police say the new footage is irrelevant to their investigation. Investigators have previously said Officer Darren Wilson initially stopped Brown for walking in the street, not because the store reported a robbery.

About 100 protesters gathered at the store Sunday night, forcing it to close, and gunshots were heard before midnight, but no one appeared to be injured, according to the St. Louis Post-Dispatch.