Parade shooting suspect expected to appear in court

Dozens of mourners gather for a vigil near Central Avenue and St Johns Avenue in Highland Park (Anthony Vazquez/Chicago Sun-Times/AP)

The man charged with killing seven people when he unleashed a hail of bullets on an Independence Day parade from a rooftop is expected in court as authorities face questions about how he was allowed to buy several guns, despite threatening violence.

Robert E Crimo III was charged with seven counts of murder on Tuesday after the shooting, which sent hundreds of marchers, parents and children fleeing in fear and set off an hours-long manhunt in and around Highland Park, an affluent Chicago suburb on the shores of Lake Michigan.