Her threat comes after people were spotted gathering in big crowds this weekend, defying the city's social distancing guidelines.
Coronavirus in Illinois: Latest news on COVID-19 cases, Chicago area impact
Police were called to gatherings like this dozens of times over the weekend, including parties where large groups of people were gathered. It was probably the nicest weekend of the year so far, which officials say is a huge challenge.
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"We don't want to be in a position where we have to arrest people for non-compliance. That's a fail. That's a fail on everybody's part - it's a fail on the person who is arrested and it's a fail on our ability as a city, as individuals, as communities to recognize the moment that we're in," Lightfoot said.
Mayor Lightfoot said she is constantly looking for people who can help relate the message about social distancing and the danger of COVID-19 to young people. She said this is a difficult group to reach to help them understand that they could bring the virus home to relatives in the home who may be at a higher risk.
"When you send the police right away, the young people feel that this is war," said State Rep. La Shawn Ford, 8th District.
Ford said people from the community need to help get the message out about the need for social distancing. And he also believes higher penalties for violating the stay-at-home orders might help.
"I don't think people are really getting the message because they haven't really felt the impact in their pocketbooks," Ford said.
Video of these large gatherings and the police response send the wrong message, according to Mayor Lightfoot. She said fines and even arresting those who violate the stay-at-home orders are the last resort. But, if necessary, she said that's what the city will do.
"We're constantly looking for credible messengers to deliver important messages that are actually going to reach out young people in particular, but we can't give up this fight against COVID," Lightfoot said.
Lightfoot likened the pandemic to a baseball game, saying we are only in the 4th inning - and it could be an extra-inning game.