When a white police officer killed an unarmed biracial teen in Wisconsin's capital city, the shooting heightened tensions and stirred up some protests.

But no one has hurled so much as a pebble, broken anything or thrown any punches. The approximately two dozen arrests so far involved protesters blocking traffic.

Instead, existing relationships, local traditions and cooler heads helped keep the streets of Madison peaceful — at least so far.

Officer Matt Kenny killed 19-year-old Tony Robinson on March 6. On Tuesday, a prosecutor announced that the officer would not be charged.

Police credit their longstanding relationships with black leaders. Chief Mike Koval reached out to Robinson's family personally, even praying with Robinson's grandmother in her driveway.

The ultra-liberal city has a long tradition of accommodating and encouraging political demonstrations.