The high powered rifle used in the Highland Park mass shooting by suspect Robert Crimo III was bought legally in Illinois, Mayor Nancy Rotering told the Chicago Tribune.
Six people were killed and dozens injured in the deadly shooting north of Chicago.
Chris Covelli, a spokesman with the Lake County Major Crimes Task Force, also confirmed the suspect who is in custody for the shooting purchased the gun in Illinois.
Details on the original purchase of the weapon came from an expedited trace conducted by the Bureau of Alcohol, Tobacco, Firearms and Explosives in the wake of the shooting.
Covelli also told the Tribune that the FBI is sending in an expert team to reconstruct the shooting, which means items left along the parade route will likely remain for several days.
The victims ranged in age from 8 to 85.
Police arrested Robert “Bobby” E. Crimo III, 22, Monday evening following an hourslong search.
He had previously been described as a “person of interest” in the case by Highland Park police. After a short chase, he was apprehended in North Chicago without incident, authorities said.
Police recovered a rifle at the crime scene.
Crimo posted online videos under the name “The Awake Rapper,” some with chilling references to violence, including one that features footage of a young man in a bedroom and a classroom along with cartoons of a gunman and people being shot.