From the Chicago Sun-Times:
Several thousand protesters spent five hours peacefully chanting, singing and marching against war. At the end, nearly 40 young veterans dramatically took their military medals and hurled them toward McCormick Place, where world leaders met behind closed doors.
It was supposed to end there — at Michigan and Cermak.
But a “Black Bloc” of about 100 anarchists wanted something else. The group, which chanted “What do we want? Dead cops!” as it left Grant Park at 2 p.m., surged to the front of the protest crowd and tried to break through the imposing line of Chicago cops in riot gear blocking its path.
Then, in a scene Chicagoans feared ever since the city learned it would host the NATO Summit, the two sides violently clashed on live TV, with police nightsticks flailing and protesters unleashing a volley of sticks, bottles and at least one rock.
The battle at Michigan and Cermak flared and then slowed, and then flared again in bursts between 5 and 6:30 p.m. By then, much of the Black Bloc had slipped away, leaving behind a scene of bloodied protesters and four injured cops, including one stabbed in the leg.