Chicago epidemiologist Gary Slutkin likens societal violence to bubonic plague in its capacity to spread uncontrollably through a cycle of retribution and domination. His urban organization, CeaseFire, tackles the Windy City's never-ending epidemic of gang violence much like a doctor might attack an outbreak: on a case-by-case basis. The group comprises reformed gangbangers and hustlers who take to the most crime-riddled areas of the city to coax enraged thugs to lay down their arms, if only for a moment. Because of their past criminal notoriety—CeaseFire workers include former vice lords, murderers and hustlers—they can often prevent gang members from pulling the trigger. Often, of course, they can't. 

Hoop Dreams director Steve James' searing new documentary, The Interrupters, follows CeaseFire's team for a year in the trenches—2009-10, when gang-related killings reportedly outnumbered U.S. casualties in Afghanistan and Iraq, and when the beating death of 16-year-old Derrion Albert caused a media storm in the projects when it appeared on YouTube. With unparalleled access, James follows three principal "violence interrupters"—charismatic reformed gang leader Ameena Matthews (daughter of notorious gangster Jeff Fort), haunted Latino murderer-turned-street-savior Eddie Bocanegra and former hustler Cobe Williams—as they mediate between various rival gangs to help prevent bloodshed.

The Interrupters is a harrowing journey through the streets, troubled high schools, the projects and the endless series of funerals of a city in turmoil—where politicians consider deploying the National Guard to quell violence, innocents are killed by stray bullets, and a shit-talking session results in one gangbanger smashing another's face with a concrete block. James' camera catches it all, from moments of unspeakable horror—such as a slain teen's memorial service where family members fear ambush by a rival gang—to moments of unexpected hope, including an ex-con's emotional apology to the family he held at gunpoint. If there's anything wrong with the picture, it's that, at 125 minutes, it's simply too short to tell all the captivating stories with the full detail each deserves.

Yet The Interrupters never becomes unfocused, nor does it relent in its portrait of entire communities held captive by impending doom. At one point, the camera pans through a tunnel where the names of dozens of murder victims are painted on the bricks. It pauses briefly on a brick that reads "I am next." It's alarming in its frankness, and that inevitability permeates every moment of The Interrupters. CeaseFire's goal is to prove the author of that grim sentence—and countless others who share that fatalism—wrong. Their work is endlessly inspiring, and James' presentation of their stories is a triumph.

94 SEE IT: The Interrupters opens Friday at the Hollywood Theatre.