The suspect, 21-year-old Robert E. Crimo III, was taken into custody on Monday after surrendering to police. Police said he had planned the attack for several weeks, and authorities were still considering what criminal charges to bring.
Police said they did not know what the motive was for the shooting.
(Additional reporting by Brendan O'Brien in Chicago, Jonathan Allen in New York and Doina Chiacu in WashingtonEditing by Alistair Bell)
By Eric Cox and Brendan O'Brien