Robert 'Bobby' E. Crimo III, the suspected shooter, was taken into custody Monday (July 4) but has not yet been charged in relation to the incident.
Crimo was spotted by police at Route 41 and Buckley Road, which led to a pursuit before his vehicle was stopped at Westleigh Road and 41 in Lake Forest.
Police said Crimo is from the area and his social media posts are part of their ongoing investigation into the incident.
Seven people died and dozens were seriously injured in relation to the shooting at a Fourth of July parade in Highland Park, Illinois, police confirmed via ABC News.
The suspect was initially described by police as a man between the ages of 18 and 20 and believed to have fired shots from a roof in what police described as a "random act of violence."
City officials also confirmed a rifle was recovered in relation to the incident, which police later described as a "high-powered rifle."
The FBI said it sent resources to the scene of the shooting.