Lightfoot announced a curfew from 9 p.m. until 6 a.m., effective immediately and "until further notice."
"What started out as a peaceful protest has now devolved into criminal conduct," Lightfoot said. "I've watched as protesters hurled not just words or projectiles at our police department, but bottles of water, urine, and lord knows what else. I saw protesters armed with shovels, bats, hammers and metal pipes."
The curfew prohibits residents from remaining "in any public place - including but not limited to streets and highways, and common areas of schools, hospitals, office buildings and shops; or on the premises of any establishment - defined as any privately owned business operated for a profit to which the public is invited, within the City of Chicago during curfew hours."
When asked how police would handle protesters who refuse to go home after 9 p.m., Lightfoot said that "they will be locked up."
The mayor said she expects "that most people who have been peaceful today will go home," and clarified that essential workers are exempt from the curfew.
Chicago police will enforce the curfew through warnings, fines or arrests, the city said.
The FBI released a statement on the unrest in Chicago Saturday night.
"The FBI is aware of the situation in downtown Chicago and working with law enforcement partners to protect our citizens and restore order to our community," a spokesperson said. "The FBI takes its responsibility to protect the civil rights of all people seriously and encourages the public to report civil rights violations at fbi.gov/tips."
Anyone in the Loop looking to return home may exit on foot via the LaSalle Street Bridge or any direction south, the city said. CTA's buses and trains are running outside of the Loop.
In order to comply with the curfew, you must be on the way home. If you are in the Loop, you may exit on foot via the LaSalle Street bridge or any direction south. @CTA buses and L stations are open and running outside of the Loop. Please be safe.— City of Chicago (@chicago) May 31, 2020
The curfew comes after thousands of demonstrators marched through the streets in Chicago's Loop Saturday to call for justice in the death of George Floyd, a black man who died after a white Minneapolis police officer pressed a knee into his neck.
Earlier Saturday, Mayor Lightfoot said the city would give peaceful protesters space.
But "we won't tolerate lawlessness," she said.
Chicago Police Department Superintendent David Brown reported that the crowd grew "increasingly more mean-spirited and violent."
ABC7's Chopper 7HD flew over crowds of demonstrators in the Loop, where the CTA has temporarily suspended service due to protest activity. The northbound lanes of Chicago's Lake Shore Drive at Roosevelt are also shut down.
[Major Delays] Loop 'L' trains are running with delays near downtown Chicago due to protest activity.— cta (@cta) May 30, 2020
Chicago police have not released any information about arrests from Saturday's protests. But chopper footage captured what appeared to be multiple people being taken in to custody, as well as damage to police vehicles, parked cars and vandalized buildings.
Near the Trump Tower, protesters spray painted Chicago police vehicles and smashed the squad cars' windows.
In the Loop, a Chicago police car was tagged with graffiti, egged and its tires were slashed.
CPD Supt. Brown was in the midst of the protests with his troops Saturday.
Earlier in the day, Brown reported that 108 people were arrested, and 12 squad cars were damaged in a similar protest Friday that carried on overnight.
"Dozens" of Chicago officers were injured during the protests on Friday, Brown said.
RELATED: Arresting officer charged with murder in death of George Floyd
Late Friday night, a crowd gathered near Trump Tower before moving down State Street into the Loop about midnight. Marchers carried signs and chanted to protest the death of George Floyd in Minneapolis police custody.
Several protesters could be seen throwing bottles, climbing onto cars and damaging property early Saturday near State and Harrison streets before officers took multiple people into custody.
Most of those arrested face disorderly conduct charges, but one individual was armed and faces additional charges, Brown said.
He also said about a dozen officers were injured. One broke a wrist, as protesters advanced on police, Brown said.
"This is hard and it's not easier when we have a president who is inciting, I think, violence. Let's be better than him. Let's be better than those who want to see us turn on ourselves, but do it in a way that's respectful," Lightfoot said.
"We believe in first amendment rights, but we also believe this is a nation of laws, but lawlessness has no place in this country," he said.
Lightfoot recalled the killing of Laquan McDonald as a painful period for the city but also a time of peaceful protest.
"This moment that we are in really has unearthed generations of pain and anger and frustration among black folks, communities of color and others around their experience of policing in America and their experience of policing in Chicago," she said.
Brown said Floyd's arresting officers are not representative of police across the country.
"We don't want our officers treating anyone like that. It's always the right time to do the right thing. Everyone deserves a measure of respect and that type of behavior in our department will not be tolerated," he said.
Chicago resident Alexander Reid wanted to personally witness the aftermath of the overnight protests.
"Nothings changed police are still killing innocent people and getting away with it for nonviolent crimes," said Reid.
Reid said he was disappointed to see people protesting for what he said are the wrong reasons.
"Someone's life was taken at the end of it and smashing windows, trying to loot businesses isn't helping anything," he said Saturday morning.
Parking will be restricted from Chicago Avenue to Ida B. Wells Drive and Lake Shore Drive to Wells Street due to protests, officials said in an alert Saturday morning.
Earlier on Friday, marchers shut down several downtown streets as protests in response to the killing of Floyd were spreading to dozens of cities across the nation.
Emotional protesters took over quieter-than-usual city streets and outmaneuvered patrolling police officers, briefly shutting down traffic to the Eisenhower Expressway.
What happened to George Floyd is reprehensible. As CPD works to ensure you have the ability to express your First Amendment rights, we ask you to do it in a safe and peaceful manner. The safety of our residents, officers and the communities we serve is our top priority. pic.twitter.com/0w6AQf52rb— Chicago Police (@Chicago_Police) May 30, 2020
African American residents in Chicago said they understand the pain and anger fueling the demonstrations a couple states over.
"You get tired of police brutality," said Edward Vaughn. "I think it's about time people started standing up for themselves."
"I am extremely frustrated, but I think at this point I am kind of numb to the situation," said Shaliah Ramsey.
Lightfoot called out President Trump for his controversial tweet about the protests, saying "when the looting starts, the shooting starts."
The phrase originates with the Miami police chief in 1967, who was talking about cracking down on African Americans during protests around the Republican National Convention, ABC News reported.
Mayor Lightfoot was direct in her response.
"I will code what I really want to say to Donald Trump," she said. "It's two words. It begins with F, and it ends with U."
"I think the state response, particularly the tweets by the president about shooting looters, also, for me, harken back very strongly to the 1960s here in Chicago," said Elizabeth Todd-Breland, UIC history professor.
Many in Chicago are relieved that charges have been filed against the former Minneapolis police officer for Floyd's killing, but journalist Jamie Kalven, who broke the Laquan McDonald story, said holding police officer accountable isn't enough.
"It was a matter of historical importance that officer Jason Van Dyke was found guilty of the murder of Laquan McDonald," Kalven said. "That didn't change the underlying system that produced Jason Van Dyke and that terrible murder."
Illinois Gov. JB Pritzker responded to the protests and events, saying, "The threat that comes to every black American under color of law that they see in a video like that, we're lucky that that video was ever taken because that is happening around America, probably every day."
Pritzker further condemned President Trump's response to the George Floyd case and the protests that have erupted in Minneapolis and across the U.S.
"From the very moment that I announced my decision to run for governor 3+ years ago, I said that this president was a racist, misogynist, homophobe, a xenophobe, and I was right then and I'm right now," Pritzker said. "His tweets, his reaction, his failure to address the racism that exists in America, it is stoking of the flames in sometimes subtle and sometimes not-so-subtle ways."
Lightfoot said the city had a plan to protect demonstrators at Friday's protest and did remind everyone coming out to protest to make sure they remember that COVID-19 is still spreading in the city, and to take precautions to keep themselves and those around them safe.
CHICAGO ACTIVIST TRAVELS TO MINNEAPOLIS TO SUPPORT PROTESTERS
Chicago activist Ja'mal Green traveled to Minneapolis to support the demonstrators, and cell phone video he took shows a police station lit on fire by protesters.
Green spoke with ABC 7 Chicago from Minneapolis Friday morning as buildings were still smoldering.
"They want to demonize these people because they're angry," Green said. "After being contained in communities with no opportunities, with no resources and dealing with a police department that are treating them like dogs and killing them with no accountability of justice. How do you expect people to feel? Have to continue to watch the brothers and sister be killed in front of them on tape? How do you expect them to feel? They're fighting like they have nothing to lose."
Reverend Jesse Jackson is also in Minneapolis, meeting with local faith leaders to encourage peaceful protesting.
Parking banned, CTA trains suspended in Loop during latest George Floyd protest
Chicago officials are restricting parking and shutting down CTA service in most of the downtown area Saturday during a Loop protest taking place in the wake of the Minneapolis police killing of George Floyd.
The parking restrictions will extend from Chicago Avenue south to Ida B. Wells Drive, and from Lake Shore Drive west to Wells Street, according to the Chicago Office of Emergency Management and Communications.
Cars found in the area will be towed to 1802 S. Lake Shore Drive, officials said.
The CTA suspended Red, Brown, Blue, Orange, Green and Pink Line service in the Loop about 6 p.m., citing protest activity in downtown.
The Orange Line is suspended between the Loop and Halsted, the Brown Line is suspended between the Loop and Chicago and the Pink Line is suspended between the Loop and Ashland, the CTA said.
The Red Line is stopped between Clark/Division and Sox-35th, while the Blue Line is stopped between Division and UIC-Halsted, the CTA said. The Green Line is suspended between Ashland/Lake and 35th-Bronzeville-IIT.
The Sun-Times Media Report and the Associated Press contributed to this article.