Police believe the gunman targeted victims at random, with no clear racial or religious motive.
A man suspected of killing six people at a 4 July parade near Chicago planned the attack for weeks, police say.
Law enforcement believe that Robert Crimo III, 21, legally bought the high-powered rifle he used in the attack.
The suspect is believed to have disguised himself in women’s clothing to escape the scene with the fleeing crowd, officials added.
Some 30 people were also injured in the shooting on Monday at Highland Park’s Independence Day parade.
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