BUFFALO, N.Y. (WIVB) — Law enforcement agencies in Buffalo are investigating whether a former federal agent knew in advance an 18-year-old white supremacist was going to attack the Tops on Jefferson Avenue, multiple sources told News 4.

This story was first reported by The Buffalo News. Law enforcement sources with direct knowledge of the investigation told News 4 the former federal agent was among a small group of people to have regular interactions online with the gunman.

About 30 minutes before he opened fire in the Tops parking lot, the shooter posted a racist diatribe and invitations to watch the massacre live on the social media site, discord.

Sources tell News 4 that the former federal agent’s relationship with the gunman is part of the ongoing investigation.

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Dave Greber is an award-winning anchor and reporter who has been part of the News 4 team since 2015. See more of his work here.