A woman wipes her tears after a mass shooting in Highland Park, Illinois.

Chicago, July 4 (RHC)-- At least six people have been killed and two dozen others injured in a shooting in a Chicago suburb, officials in the U.S. city of Highland Park, Illinois, said after a gunman opened fire from a rooftop on an Independence Day parade.

Officials said during a news conference on Monday that six people were dead and 24 were taken to hospital after the mid-morning attack, and that a rifle was recovered from the scene.  A hospital spokesperson reported 31 people were injured.

Hours after the shooting, authorities continued to search for the suspect, who was described as a white male wearing a white or blue T-shirt and is believed to be about 18 to 20 years old.

Lake County Major Crime Task Force Spokesperson Christopher Covelli told reporters the gunman apparently used a “high-powered rifle” to fire from a spot atop a building where he was “very difficult to see.”  “Very random, very intentional and a very sad day,” Covelli said.  “We are aggressively looking for the individual who’s responsible,” he added.  “He could be in the city.  He could be somewhere else.”

The shooting comes as the United States struggles to stem a surge in gun violence and after a string of recent deadly incidents, including a massacre at a Texas primary school, has renewed calls for stricter gun regulations in the country.

The attack in Highland Park, a community of about 30,000 residents some 40 km (25 miles) north of Chicago, sent hundreds of parade attendees -- some visibly bloodied -- fleeing in panic, with many leaving behind chairs, baby strollers and blankets.   Witnesses described seeing bloodied bodies covered with blankets.

“Our community was terrorised by an act of violence that has shaken us to our core. Our hearts go out to the families of the victims during this devastating time,” Mayor Nancy Rotering told reporters later on Monday afternoon.

The Chicago Sun-Times newspaper reported that the parade began at about 10 am local time (15:00 GMT) but was suddenly halted 10 minutes later after shots were fired.

Amarani Garcia, who was at the parade with her young daughter, told the local ABC affiliate she heard gunfire nearby, then a pause for what she suspected was reloading, and then more shots again.  There were “people screaming and running.  It was just really traumatising,” Garcia said.  “I was very terrified.  I hid with my daughter actually in a little store.  It just makes me feel like we’re not safe anymore.”

Debbie Glickman, a Highland Park resident, said she was on a parade float with coworkers and the group was preparing to turn onto the main route when she saw people running from the area.   “People started saying: ‘There’s a shooter, there’s a shooter, there’s a shooter,’” Glickman told the Associated Press news agency.  “So we just ran.  We just ran.  It’s like mass chaos down there.”