Twenty-one police officers were injured during an overnight spree of protests and violence that started as a demonstration over the police killings of Philando Castile and other African-Americans. The protesters shut down a section of Interstate 94 in St. Paul for more than five hours overnight.

The interstate was closed in both directions between downtown and Minnesota 280 from about 8 p.m. Saturday to 1:15 a.m. Sunday. St. Paul police said objects thrown at officers injured 21 of them. Police arrested 102, at the interstate and later after a group marched down Grand Avenue.

“This has been a very, very long evening and early morning in the city of St. Paul,” Mayor Chris Coleman said Sunday morning. “As many of you have seen from the footage, we had an extreme incident last night following what has been several days of peaceful protest in the city of St. Paul.” At least three of the injured officers were sent to hospitals, he said.

From a truck parked in the eastbound lanes, protest organizers chanted slogans, spoke of racial injustice and urged the crowd to remain peaceful. The group mostly complied early on, but later into the night, police were targeted with rocks, fireworks and construction rebar taken from the roadway.

Scores of white demonstrators stood side-by-side at the perimeter to protect others from arrest. Many were taken into custody.

“There’s a part of my community that’s hurting, and I’m here to support them,” said Brendan Kelly, 38, who carried a sign that read “Justice for Philando.”

Hundreds more watched the demonstration from the grass on either side of the highway and on bridges over the road.

Once the heart of St. Paul’s predominantly black Rondo neighborhood, the site of the protest has historic significance to the city’s African-American community. Many of its residents were displaced when I-94 was built in the 1960s, devastating the once-vibrant neighborhood.

Castile, a 32-year-old black man from St. Paul, was shot and killed by a St. Anthony police officer during a traffic stop Wednesday in Falcon Heights, just north of St. Paul. Tensions between police and protesters were high Saturday as demonstrations over his death reached a fourth day.

After ordering protesters to disperse more than 25 times, officers wearing riot helmets and gas masks fired smoke rounds and chemical irritants at the crowd, and less-lethal marking rounds at the people they believed were throwing things at them.

Austin Jackson, 19, said police pepper-sprayed him and children who were in a vehicle on the interstate. Jackson said the children had been placed in the vehicle to remove them from the protest, but the vehicle was blocked by police on the Dale Street exit ramp.

“Eight-year-olds got hit with Mace,” he said.

Steve Linders, a St. Paul police spokesman, said Sunday morning that “officers did not spray Mace into the faces of children.”

Police did spray chemical irritant while protesters had the highway shutdown, but Linders said he didn’t know if it was used around the truck of protesters that had children inside.

“But I do want to say that the people who made the decision to bring children onto the interstate made the decision not to get their children off the interstate after police directed them to multiple times,” Linders said. “Had they not made that decision … their children would not have been put in harm’s way.”

Officers from several nearby cities were on hand to assist St. Paul police and Minnesota State Patrol troopers in dispersing the crowd and making arrests. In all, about 200 officers were involved. There were 50 arrests made on the interstate.

The interstate was cleared of protesters by 12:30 a.m. Sunday, allowing plows to clear debris off the roadway.

Afterward, many of the protesters returned to the Minnesota governor’s residence on Summit Avenue, were there were renewed calls for peaceful protests. About 2 a.m., a group of fewer than 100 protesters left the mansion and marched east on Grand Avenue for several blocks, loudly chanting, “We’re just taking a walk! We’re just taking a walk!”

Police and state troopers met them at Dale Street about 2:45 a.m. and took between 40 to 50 into custody.

Police said they made 50 arrests on the interstate and another 52 later on Grand Avenue. Those on the highway were booked on third-degree rioting; those on Grand Avenue were tagged and released, officials said.

Earlier Saturday, vigils and rallies for Castile were held elsewhere in the Twin Cities.

A nearly all-white congregation of about 170 filled Falcon Heights United Church of Christ for an evening service of “prayer and lament,” a half-mile from where Castile was killed.

The Rev. Anne Swallow Gillis led them in prayer for “the marginalized and the oppressed among us.” She encouraged them to feel the pain of Castile’s death and those of Alton Sterling in Louisiana and the five police officers in Dallas.

“God, in Your mercy, show me my own complicity in injustice,” they prayed. “Convict me for my indifference. Forgive me when I have remained silent.”

Emily Hill, 18, said she was at home during a power outage Wednesday night when she heard the shots that killed Castile and guessed they were fireworks. When she learned otherwise the next morning, the nation’s angst over the often deadly interactions between police officers and people of color came into sharp relief.

“To find out that that was what we heard a few blocks down the street was heartbreaking,” she said after attending the special church service in her neighborhood Saturday evening.

Barb Carmouche, 62, of South St. Paul attended because prayer is “all I can do right now,” she said.

Carmouche is white but has black children and grandchildren. She left the service in tears, thinking of the challenges her children faced in their youth because of their skin color.

“I thought I had already fought this battle for them,” she said. “I never thought I would see it again, and I’m seeing it right now.”

Kevin Nelson, 52, of St. Paul was one the few black faces at at the church, where he performed a solo of “If I Can Help Somebody,” a song favored by Martin Luther King Jr.

Nelson grew up in the suburbs of St. Louis, has mostly been around white people all his life and has rarely felt mistreated because of his skin color. But that’s changed over the past decade or so.

“I think I’m starting to pay attention to it,” he said.

Hundreds also demonstrated Saturday at Loring Park in Minneapolis for a Day of Atonement Solidarity Rally. Following the roughly 90-minute rally, demonstrators marched through the city’s downtown to the Basilica of St. Mary, where the Basilica Block Party music festival was underway.

Gov. Mark Dayton, who had addressed protesters on his lawn early Thursday morning and raised eyebrows when he said Castile likely would not have been shot if he were white, met with the dead man’s family and friends Saturday.

He and Lt. Gov. Tina Smith met privately with the group, according to Matt Swenson, the governor’s spokesman. Swenson said the meeting was “very cordial,” but Dayton would not comment further.

According to Dayton’s schedule, he will meet with Cornell Brooks, the president of the NAACP, on Sunday.

An investigation has begun into Castile’s death, which happened during a traffic stop in Falcon Heights on Wednesday night. The aftermath of the shooting was live-streamed over Facebook and has been shared nationwide. His death has been mentioned by protesters who have taken to the streets not only in the Twin Cities, but in Dallas and other cities across the country.

Meanwhile, the Minnesota Lynx basketball team wore special black warm-up shirts to their game against the Dallas Wings on Saturday night in honor of Castile, Sterling and the Dallas Police Department.

Printed on the front of the shirts were the words, “Change starts with us. Justice & Accountability.” Castile’s and Sterling’s names were on the back, above the Dallas Police Department’s logo.