Six dead in 4 July parade shooting near Chicago

The event in the city of Highland Park was suddenly halted shortly after 10:00 local (15:00 GMT), when several shots were heard.

Residents have been urged to stay at home and contact their loved ones to make sure they are safe.

City authorities said 24 people had also been hospitalised.

"We are aggressively looking for the individual responsible for this shooting," Lake County Major Crime Task Force spokesman Christopher Covelli told reporters.

Chicago goes high-tech in search of answers to gun crime surge

Somewhere in the district a microphone has picked up the percussive sound of a bullet and sent a signal, via California, to the station, which is where Kim Smith hears about it.

Ms Smith, a data analyst from the University of Chicago, works at one of the city's new Strategic Decision Support Centres, where data, technology, and old-fashioned police work are being combined in an effort to control a sudden surge in gun violence.

Chicago man cleared after 17 years in prison shot dead

Chicago police spokesman Anthony Guglielmi (gooh-YEHL'-meeh) says 40-year-old Alprentiss Nash was killed Tuesday after arguing with his attacker.

He says police are questioning a person of interest.

Nash was convicted in the 1995 murder of Leon Stroud on Chicago's South Side, based on witness testimony. In 1997, he was sentenced to 80 years in prison.