A prosecutor in Wisconsin said that a police officer in Madison, Wis., will not face criminal charges for fatally shooting an unarmed man earlier this year.

The decision came more than two months after Anthony Robinson Jr., 19, was shot by Matthew Kenny, 45, as the police officer responded to calls about a disturbance.

“I conclude that this 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.,” Ismael Ozanne, the Dane County district attorney, announced Tuesday afternoon at a news conference.

Local authorities say they have prepared for protests that could follow the announcement, which comes amid increased scrutiny on how police use lethal force. Over the past several months, protests have erupted in multiple cities — including Madison — after deaths at the hands of police.

Robinson’s March 6 death prompted days of sustained, peaceful demonstrations in Wisconsin’s second-largest city. Police say they were responding to multiple calls about a disturbance involving Robinson, including calls that said he had assaulted other people and run into traffic.

In a brief statement after the shooting, police said that when they found Robinson, “a struggle ensued” and he was shot. Kenny was placed on paid administrative leave, and the police chief apologized for the shooting and asked for patience during the investigation.

Robinson’s death was investigated by the state Division of Criminal Investigation, because Wisconsin has a law requiring an outside agency to look into officer-related deaths.

The state’s investigation involved dozens of interviews with witnesses and another series of interviews with residents of the neighborhood, the agency said. Once the agency completed its investigation, it turned over the details to the district attorney to decide whether to file any charges.

“At the end of the day, this is a human tragedy for Tony Robinson’s family and for the police officer involved,” Brad Schimel, the Wisconsin attorney general, said in a statement shortly after Robinson’s death.

Ozanne, who was appointed in 2010, is a lifelong Madison resident and the first black district attorney in Wisconsin history, according to his office. He said he viewed his responsibilities through this lens as “a man who understands the pain of unjustified profiling” and described discussions he has had recently with community members who are distrustful of the criminal justice system.

“My decision will not bring Tony Robinson Jr. back,” Ozanne said Tuesday. “My decision will not end the racial disparities that exist in the justice system, in our justice system.”

He described his review of the evidence as methodical, outlining a process that involved sifting through 800 pages of reports, viewing surveillance footage and interviewing residents, police officers and emergency responders.

Ozanne said that the evening of the shooting, three calls were made to 911 within four minutes, all reporting issues involving Robinson.

The first call came from a friend of Robinson’s who reported that the 19-year-old “was tweaking” after taking mushrooms, Ozanne said.

The prosecutor also described calls about an unarmed man who matched Robinson’s description punching a pedestrian in the face and another call from someone who said Robinson had tried to choke him. Robinson was also seen trying to assault people on the sidewalk and blocking traffic, Ozanne said.

Toxicology reports later confirmed that Robinson had mushrooms, marijuana and Xanax in his body at the time of his death, according to Ozanne.

Kenny, who was interviewed by prosecutors, said he heard “incoherent yelling and screaming” from an upstairs apartment when he arrived, according to Ozanne. Kenny said that when he went up the stairs,  Robinson hit him in the head and knocked him into a wall, Ozanne said. The officer said he opened fire after fearing that he would be hit again and his gun could be taken and used to shoot him or others.

Kenny fired seven shots in three seconds, and all of the shots hit Robinson on the front of his body, Ozanne said.

After the shooting, Kenny said, he did not know how he got to the bottom of the stairs but that Robinson was still conscious at the time. Kenny said he tried to give first aid to Robinson until the paramedics arrived, Ozanne said.

“A young man lost his life far too soon,” Ozanne said. He urged people to respond without any violence.

Michael Koval, the Madison police chief, released a lengthy statement after Ozanne announced his decision, again offering his condolences to Robinson’s family.

“As a father of two adult sons, I cannot begin to grasp at the magnitude of their loss,” Koval wrote. “The difficulties that they have faced have been formidable and I hope that some measure of healing can begin.”

Kenny will remain on administrative leave until the police department finishes an internal review to determine whether any of its procedures were violated, Koval said.

In his statement Tuesday, Koval wrote that Madison “finds itself at a crossroad” after the decision. Protesters can respond with the property damage and disorder seen in other cities, he said, or they can “take the higher road” of nonviolent civil dissent and civil disobedience.

“Unrest like we have witnessed elsewhere in our country cannot possibly aid in constructive engagement and only holds us back,” Koval wrote. “The environment for healing and reconciliation has been forged, owing to the incredible capacity of the Robinson family and their urging of the community to deal with the issues at hand with responsible activism.”

In addition, Koval detailed what kinds of protest activities are legally allowed and what types of activities could lead to fines or jail time for protesters. He wrote that some people will choose to get arrested and called that “a hallmark of civil disobedience,” though he encouraged people to violate city ordinances (which carry fines) rather than committing misdemeanors or felonies (which lead to jail time).

The American Civil Liberties Union of Wisconsin said the decision “leaves a cloud of uncertainty” over who is responsible for Robinson’s death.

“If Officer Kenny did not violate the law, then is anyone legally responsible for Mr. Robinson’s death?” Chris Ahmuty, the group’s executive director, said in a statement. “Does the criminal law protect individuals like Mr. Robinson from deadly force exercised by police officers? Are police officers above the law?”

Decisions not to charge officers in Ferguson, Mo., and New York City last year were followed by heavy protests in those cities.

The Young Gifted and Black Coalition, a group that organized protests after Robinson’s death, said it planned to hold a march on Wednesday. The group earlier posted on Facebook that it did not expect charges against Kenny but said it did not plan to lead any activities on Tuesday out of respect for Robinson’s family.

Jim Palmer, executive director of the Wisconsin Professional Police Association, released a statement calling the decision “appropriate,” saying that Kenny was acting in response to a deadly threat.

City officials said police in Madison have spent weeks preparing for the announcement and meetings with community leaders.

“It is our hope — that working together — Madison can come through these challenging days ahead without violence or property damage,” the city said in a statement.

In the days after Robinson’s death, protests in Madison stretched into the state capitol, with demonstrators marching from the University of Wisconsin’s campus to the capitol’s rotunda. Madison authorities said they know protests could follow the decision about charges, and they vowed that police will help demonstrators march safely in the city.

“It is our belief that Madison can endure without being fractured,” the city’s statement said.

After Robinson’s death, the police chief, mayor and other city leaders described the shooting as a tragedy, promised answers and called for changes. This quick response underscored what observers say is a changed atmosphere since last summer’s initial protests in Ferguson, as authorities have tried to act quickly to avoid unrest.

Madison schools are planning on providing “structured opportunities” for students to discuss the decision once it is announced, according to the school district.

In addition, the district said that while middle and high school students may want to participate in protests, it has urged parents to encourage their children to remain in class during the school day.

“While we have been proud of how responsibly and safely our students have participated in events throughout the community, we also think it is important for you to talk with your child about both their rights and responsibilities as part of a protest if they choose to participate, as well as the consequences of a possible arrest,” Jennifer Cheatham, superintendent of the Madison Metropolitan School District, wrote in a message to families in the community.

This post has been updated with the prosecutor’s decision. First posted: 12:22 p.m.