Detectives met with the 14-year-old girl and her mother at their home on Sunday after identifying her as a possible suspect and the possible origin of a threat, which was shared on social media.
Officers searched the girl's room and did not find any weapons. Detectives questioned her at the Joliet Police Department before releasing her. Officers did not find any evidence of a credible threat at the time, police said.
However, the 14-year-old's mother took her back to the Joliet Police Department on Monday afternoon.
During questioning, the girl, a Joliet West High School student, indicated that she was involved in creating the bogus threat on social media, police said.
Officers then placed her into custody. The 14-year-old has been charged with Felony Disorderly Conduct - Transmitting a Threat of Destruction of School Property or Violence, Death or Bodily Harm Against Persons at School.
Police said a 12-year-old girl was also arrested after police learned of an additional social media threat involving Joliet's Dirksen Junior High School.
Officers identified the 12-year-old as the person responsible for the threat, which was determined to be unfounded.
Officers placed the 12-year-old into custody at her home. She was processed at the Joliet Police Department for Felony Disorderly Conduct before being released to a parent.
Police said no evidence of a credible threat was found throughout their investigation.
Officials said one of the online threats had stated that armed students would be inside all of Joliet's schools.
Despite assurances from police and the school district that things would be made safe for students at Joliet's Central High School, most appeared to have stayed home Monday as police continue to investigate.
School buses arriving at Joliet's Central High School Monday morning were mostly empty. A trickle of students was seen entering the campus here and there.
"There usually be a lot of people right now and ain't nobody really here," Joliet Central sophomore Jerkur Sellers said.
One school bus driver told ABC7 that only five of his usual 35 students showed up. Coffee shop owner and mom Amber Duffy is among the parents choosing to be safe, rather than sorry.
"He was a little scared and what's going to happen?" Duffy said. "His friends are texting him saying their moms are letting them stay home. Their fathers are letting them stay home, so I went with my gut feeling and the safer route of staying home as well."
Disclosing the threats over the weekend, Joliet police said they surfaced online, adding that while there doesn't appear to be any credible evidence to support them, additional security measures would be taken.
Joliet Public School District 86 reverted to e-learning for Monday.
Meanwhile, Joliet Township High School District 204's two schools searched students as they arrived for class.
"I see it from the teacher perspective and from the parent perspective," parent and teacher Favio Lopez said. "Threats like this we can never take to lightly. Because if we take them too lightly and then something happens then people are hurt."
Those who did show up for school Monday said they are not worried.
"I feel it was probably some kids who were trying to stay home from school or something like that. I don't think it's real," Sellers said. "Ain't nobody going to do that.
Joliet Township High School remained open on Monday, but there were changes.
As of now, it appears Joliet schools will be back on a normal schedule Tuesday.
Plainfield's Troy Community Consolidated School District 30-C also reverted to remote learning on Monday due to a threat. Plainfield police have not provided information about possible suspects linked to that threat.