Watch How People Reacted on Twitter to the Ferguson Grand Jury Decision

Heat map shows how the conversation surged through the night.

— -- A heat map shows how the Twitter conversation about Ferguson spread across the country on Monday night following the grand jury's decision not to indict Officer Darren Wilson in the shooting death of unarmed teenager Michael Brown.

The conversation surged after 9 p.m. ET, when St.Louis County Prosecutor Robert McCulloch announced that a grand jury had decided not to indict Wilson on any of the five criminal counts they considered relating to Brown's death.

More than 3.5 million tweets sent Monday night mentioned the Ferguson decision, according to Twitter.