The suspected gunman who opened fire on a July 4 parade in a wealthy Chicago suburb planned the attack for weeks and wore women’s clothing to aid his escape, police said Tuesday. Robert Crimo, 21, whose family lives in Highwood, just north of Highland Park, where the shooting occurred, was arrested on Monday after six people were killed and more than 30 wounded during an Independence Day parade. The death toll rose to seven on Tuesday after one of the wounded victims died in hospital. Crimo was charged on Tuesday with seven counts of first-degree murder, prosecutors said. Deputy police chief Christopher Covelli said no motive had been established for the attack, in which the gunman sprayed the crowd with dozens of semi-automatic rounds fired from a rooftop. “We do believe Crimo pre-planned this attack for several weeks,” Covelli said. “He brought a high-powered rifle to this parade, he accessed the roof of a business via a fire escape ladder and began opening fire.” “Crimo was dressed in women’s clothing and investigators believe he did this to conceal his facial tattoos and his identity and help him during the escape with the other people who were fleeing the chaos.” Covelli said the gunman fired more than 70 rounds from a rifle “similar to an AR-15” that he had bought legally. Authorities are investigating disturbing online posts and videos made by Crimo, who was captured about eight hours after the shooting following a brief car chase. A peek into the world of the suspected US July 4 gunman The shooting has left the upscale suburb in shock. “We’re all still reeling,” Mayor Nancy Rotering told NBC’s Today show. “Unbelievable shock,” Rotering said. “Everybody knows somebody who was affected by this directly.” The mayor said she personally knew the suspected gunman when he was a young boy in the Cub Scouts and she was a Cub Scout leader. “How did somebody become this angry, this hateful to then take it out on innocent people who literally were just having a family day out?” Rotering asked. David Baum, a doctor whose two-year-old was in the parade, witnessed the shooting and helped treat some of the injured. “The people who were gone were blown up by that gunfire,” Baum told CNN, calling it a “horrific scene”. On Tuesday, police and FBI agents were sifting through belongings left behind by members of the crowd as they fled. Strollers, bicycles, folding chairs and other items littered the parade route through the main street of Highland Park. Crimo, whose father unsuccessfully ran for mayor and owns a store in Highland Park called Bob’s Pantry and Deli, was an amateur musician billing himself as “Awake the Rapper”. The younger Crimo’s online postings include violent content that alluded to guns and shootings. One YouTube video posted eight months ago featured cartoons of a gunman and people being shot. A voice-over says: “I need to just do it.” It adds: “It is my destiny. Everything has led up to this. Nothing can stop me, not even myself.” Biden tries to sound upbeat on July 4, despite 309 US mass shootings this year Crimo, who has the word “Awake” tattooed over an eyebrow, is seen sporting an “FBI” baseball cap in numerous photos and is wearing a Trump flag as a cape in one picture. The shooting is the latest in a wave of gun violence plaguing the United States, where around 40,000 deaths a year are caused by firearms, according to the Gun Violence Archive. The Highland Park shooting cast a pall over Independence Day, when towns and cities across the United States hold parades and people attend barbecues, sporting events and fireworks displays. In another July 4 shooting, two police officers were wounded when they came under fire during a fireworks show in Philadelphia.