A white Wisconsin police officer won't be charged for fatally shooting an unarmed 19-year-old biracial man, a prosecutor announced Tuesday, prompting peaceful demonstrations but none of the immediate violence that has hit some other U.S. cities.

Dane County District Attorney Ismael Ozanne said he wouldn't file charges against Madison Officer Matt Kenny in the March 6 death of Tony Robinson, saying the officer used lawful deadly force after he was staggered by a punch to the head and feared for his life.

Ozanne, mopping his brow repeatedly but speaking forcefully for some 25 minutes, took pains to outline his own biracial heritage before announcing his decision.

"I am the son of a black woman who still worries about my safety," Ozanne said. "I am a man who understands the pain of unjustified profiling and I am the first district attorney of color not only in Dane County but in the state of Wisconsin."

Then, Ozanne walked through evidence from the scene, 911 callers, Robinson's friends, police affidavits, crime lab reports and more to paint a picture of a young man out of control from a mix of hallucinogenic mushrooms, marijuana and Xanax. Officer Kenny rushed to the apartment building, and immediately became concerned that Robinson was attacking someone upstairs. He fired his weapon only after he was punched in the head and feared he might be disarmed and killed, Ozanne said.

"I conclude that (Robinson's) tragic and unfortunate death was the result of a lawful use of deadly police force and that no charges should be brought against Officer Kenny in the death of Tony Robinson Jr.," Ozanne said. He quickly wrapped up and left to meet Robinson family members.

Robinson's mother, Andrea Irwin, said she was not surprised by the decision. The investigation wasn't thorough enough, she said.

"They could have done a lot. What they didn't do was give my son any respect," she said. But family members, as they have since the shooting, asked that protests remain peaceful.

About 100 people gathered at Robinson's apartment house in the wake of Ozanne's decision. One of them, Jivonte Davis, 19, said he had known Robinson since the fifth grade.

"I can go out and break stuff and do anything I want right now," Davis said. "But rioting and everything, what would that achieve? We're no Ferguson, we're no Baltimore. We're going to do this the right way. We're going to do this peacefully."

The protesters, eventually estimated by police at 250 to 300 people, began marching to the state Capitol about a mile a half away. Some had dogs and strollers and were bound for a nearby church for a prayer service. Marchers chanted "No justice, no peace, no racist police," and held a banner that read "Justice for Tony." They eventually dispersed.

One lead group in organizing earlier protests, the Young, Gifted and Black Coalition, had earlier announced plans to demonstrate on Wednesday.

Robinson's death forced Madison — a liberal bastion that is home of the University of Wisconsin and the state capital — to confront racial divisions. Blacks make up about 7 percent of the population but more than that in arrests, incarceration and poverty. One demand from the Young, Gifted and Black group was to drop plans to renovate the county jail and free 350 black inmates.

Police Chief Mike Koval wrote in a blog post following Ozanne's announcement that the city was at a crossroads, with the chance to show that "civic dissent and even acts of civil disobedience" can co-exist with police. Koval's post included how protesters could avoid the most damaging arrests, and he posted a list of ordinance violations, misdemeanors and "protected activities" complete with fine amounts for the violations.

But police were also ready for the possibility of violence. A Madison police captain warned city leaders before Ozanne's decision that police had received threats from reliable sources that gang members planned violence against police officers, according to an email sent the leaders provided to The Associated Press.

The shooting was another in a series of police confrontations that have ignited racial tension across the nation in the past year. Most recently in Baltimore, riots erupted after the funeral for Freddie Gray, a black man who suffered a fatal spinal injury while in police custody. Other high-profile cases of officers killing unarmed black residents include the deaths of Michael Brown in Ferguson, Missouri; Eric Garner in New York City; and Walter Scott in North Charleston, South Carolina.

Six officers involved in Gray's death have been charged, as has the officer who killed Scott. Grand juries declined to charge the officers involved in Brown's and Garner's deaths.