Video (00:32) : 10-year old Taye was the focal point of a rally organized by Black Lives Matter and the Black Liberation Project in the boy's honor a day after being maced.

Minneapolis authorities launched an investigation into police response during a downtown street protest that turned unruly Wednesday night in which chemical spray used by officers hit a 10-year-old boy.

Police Chief Janeé Harteau and Mayor Betsy Hodges called a news conference Thursday asking witnesses to come forward.

“It is critical for everyone involved that we complete a thorough investigation, so I need the public’s help,” the chief said. “We must have the full set of facts.”

In a police report, authorities said the protesters Wednesday night repeatedly “engaged motorists, jumping on cars and trying to pull open doors. Officers pushed back the crowds to get the motorists out of harm’s way. … Chemical aerosol was used to drive back the hostile crowds.”

About 100 people closed down two blocks of downtown during the protest, which had as its focus the March shooting death of a black youth, Tony Robinson, by a white police officer in Madison, Wis. On Tuesday, authorities decided the officer would face no charges.

Susan Montgomery, the mother of the boy who was sprayed, said that she and her son, Taye, were among the protesters.

Video (00:46): Mother says 10-year old son Maced by Minneapolis police Video (00:46): Mother says 10-year old son Maced by Minneapolis police

Montgomery, of St. Paul, said the officer had been near her group of fewer than 10 protesters for some time.

At one point, the officer drove up abruptly to Montgomery and the others with his siren on and lights flashing on S. 7th Street. “People started running. It seemed like he was mad at that point,” she said.

After stopping, the officer “just jumped out of his car and started spraying everybody,” Montgomery said.

Other protesters confronted the officer, screaming that he had sprayed a child, Montgomery continued. The officer responded by spraying them as well, she said.

Taye, who his mother said is autistic, fell to the ground and was carried into a nearby hotel. Milk was poured into his eyes to deaden the chemical irritant, his mother said.

Asked Thursday about the incident, Taye told reporters, “He didn’t give us any warning. He just went right ahead and sprayed. … It hurt!”

“It made me really nervous,” he said, “because I couldn’t see where I was going. I couldn’t find my mom.”

The Office of Police Conduct Review has opened an investigation.

Harteau said she spoke with Montgomery. “We are both mothers, and we had a good conversation,” she said.

Newly elected Minneapolis NAACP President Nekima Levy-Pounds said on her Facebook page Thursday morning that the group would stand in solidarity with Taye “and other victims of police abuse here and around the country.”

Harteau and Hodges asked that protesters get in touch with them before other marches and demonstrations are carried out.

“We are proud of our history of peaceful demonstrations,” Hodges said. “Folks who are protesting tonight please get in contact.”

Minneapolis police union president-elect Lt. Bob Kroll said police are not at fault.

“There was a lot of criminal activity that shouldn’t be overlooked,” he said.

Kroll cautioned that people shouldn’t jump to conclusions and predicted that the investigation would show the actions by police officers during the protest were reasonable.

“Why is a 10-year-old at a protest at that time at night?” Kroll asked.

Minneapolis Police Chief Janeé Harteau, left, and Mayor Betsy Hodges, speak at a news briefing Thursday about a protest the previous night in downtown Minneapolis.

Taye’s mother on Thursday defended her choice to bring her son to the previous night’s protest, saying she wanted to instill a sense of social justice in him.

“If people want to call me a bad mother for taking my son there and fighting for justice, then so be it,” she said. “But I think I’m doing the best thing that I can to break cycles and make change.”

Around 75 people gathered in the rain Thursday evening to stand with Montgomery and her son, many calling for MPD to fire the officer who sprayed Taye. It was a peaceful protest that involved speeches, song and a march around downtown — blocking traffic and, at times, the light rail.

Protesters formed a square at the intersection of Hennepin Avenue and N. 4th Street for more than 10 minutes, where they held hands.

Jay Matthews, 30, who lives in downtown Minneapolis, showed his support Thursday because what happened to Taye was “unacceptable.”

“I believe there should be stronger penalties for officers because of the oath they take,” Matthews said, “because when they aren’t held accountable for their actions, it fuels a cycle of mistrust.

“In my neighborhood, calling the police is a last resort.”

10-year-old Taye was embraced by his mother, Susan Montgomery, at the demonstration Thursday night in Minneapolis.

Staff writer Liz Sawyer contributed.