Authorities detained a person of interest in the deadly Fourth of July parade shooting Monday evening in Lake Forest, Illinois.

Police detained 22-year-old Robert E. Crimo as a person of interest in the deadly massacre after a brief pursuit, authorities said. A Chicago police officer spotted Crimo and attempted to perform a traffic stop when the 22-year-old fled, authorities said, according to CNN. Crimo, who goes by the name “Bobby,” was believed to be armed and dangerous at the time he was taken into custody.

At least six people were killed and dozens of others were wounded during the shooting, according to the Chicago Sun-Times. It is believed the gunman open fired while standing on a roof.

“The police started reacting and I saw some people falling,” 57-year-old Jeff Leon, who attended the parade with his family, told CNN. (RELATED: REPORT: UFC Star Kevin Holland Stops Shooting In Texas)

“We just took off. And, you know, we, we were hiding behind cars, folding into the next car and making our way,” Leon told the outlet.

Video footage posted to social media captured the sound of the gunfire and the harrowing moments that unfolded as people began to scurry for cover and scream in terror.