Outraged by the arrest of two nurses and a union organizer volunteering at the Occupy Chicago protest over the weekend, National Nurses United is planning a protest at Mayor Rahm Emanuel's office today.



The group, the nation's largest union of registered nurses, is calling on its membership in Chicago to picket City Hall this morning to demand that misdemeanor trespassing charges against the nurses and all of the protesters be dropped.



The two nurses arrested were among a larger group marching with Occupy Chicago protesters and later set up a tent to provide first aid.



"It was the wrong move," RoseAnn DeMoro, the group's executive director, said Sunday. "We were there to make sure if the occupiers get harmed, they have first aid."



DeMoro said the nurses' arrest will only serve to strengthen her organization's commitment to the Occupy movement.



"The nurses are angry, and it's made us double our resolve," she said.



DeMoro said nurse volunteers have set up tents at Occupy protests in San Francisco, Los Angeles and New York without any arrests.



Occupy Chicago protesters, angered by what they characterized as harsh treatment by police, voted late Sunday to join the nurses' demonstration.



By 8:30 p.m. Sunday, police said almost all of the 130 people arrested the night before had been released on bail, but some remained in custody.



Police confirmed that several of the protesters arrested Saturday night were also charged in the first round of Occupy Chicago arrests last weekend. Those people are being held on bail violations, Officer Daniel O'Brien said.



It's likely that the protesters arrested for a second time will remain in jail until they go before a judge at a bond hearing, police said.



The legal stakes were higher for those who stood their ground Saturday than for the first 175 people arrested, who were given a court date and quickly released.



"I don't think a lot of people were ready for what happened," said Keith Moens, an out-of-work Chicago Public Schools teacher. "It was scary."



The protesters spent several hours in four large holding cells at the police station before being fingerprinted, photographed and booked into jail, Moens said. There they waited while police ran background checks, he said.



"I didn't intend to get arrested," said Moens, 60, of Arlington Heights. "I got caught up in the moment with all of these kids."



Moens said had he known what was in store for him, he would have left the park to avoid arrest.



A small contingent of Occupy Chicago organizers gathered outside the police station where the protesters were being held Sunday afternoon. They cheered as protesters trickled out of the jail.



"This is an attack on the core of what it means to be an American citizen," said protester Patrick Robinson, 24. "We condemn (Emanuel's) gross violation of the human rights of those arrested."



On Sunday evening, Chicago police issued a statement defending its handling of the protest.



"The Chicago Police Department works diligently to safeguard the constitutional rights of all persons. Members of the Chicago Police Department uphold the highest standards of police conduct, and this extends toward individuals in the exercise of their First Amendment rights," the statement said.



Humboldt Park resident Kate Palmer said she is not deterred by her night in jail.



"I am proud of what we're doing, and I would do it again," said Palmer, adding that she believes police are dealing with protesters more harshly to discourage others. "There will be more arrests."



Tribune reporter Ryan Haggerty contributed.