Robert "Bobby" Crimo III, who grew up in Highland Park, where the shooting occurred, was arrested on Monday after six people were killed and two dozen injured during an Independence Day parade.

Crimo was taken into custody after law enforcement launched a  massive manhunt for the gunman who sprayed paradegoers with dozens of semi-automatic rounds from a rooftop, turning the celebration into a scene of death and trauma.

"We're all still reeling," Highland Park Mayor Nancy Rotering told NBC's Today show on Tuesday.

"Unbelievable shock," Rotering said. "Everybody knows somebody who was affected by this directly."

Rotering said she personally knew the suspected gunman when he was a young boy in the Cub Scouts and she was a Cub Scout leader.