More than a dozen juveniles and one adult in Georgia have been arrested and accused of making school threats in the days after four people were killed and nine others were injured in a shooting at Apalachee High School.

The students — who range in age from 11 to 17 — were arrested in Clarke, Forsyth, Gwinnett, Hall, Hart, Jackson, Newton and Oconee counties and charged with making terroristic threats. If convicted of a felony charge, they could face fines or jail time, in addition to discipline from their schools.

“You’ve got these 11- and 12-year-old kids that don’t understand the consequences and the far reach of what their words can cause,” Oconee County Sheriff James Hale told The Atlanta Journal-Constitution. Two Oconee County Middle School students were charged after making potential threats of school violence. “These kids don’t understand that by saying that, it puts into motion a machine that is a runaway train sometimes.”

A 14-year-old was arrested and charged with murder after allegedly killing two students and two teachers at Apalachee High in Barrow County on Wednesday. In the immediate aftermath, threats started surfacing around the state, sometimes mentioning specific schools. School was canceled in Franklin County on Friday due to “online threats made directly” toward the school system. Officials in Fulton County are investigating online threats made to several of its schools.

The Monroe County Sheriff’s Office announced Chris Cooper, 26, of Jackson, was charged Friday with dissemination of information relating to terroristic acts after an investigation into threats of violence against the school district in that county.

Two high school students face criminal charges in Gwinnett County, the state’s largest district, after making threats. One student admitted they were seeking attention, according to a news release from the school system. The other told investigators they did it to avoid going to school.

“Students must understand that these actions have real consequences up to and including criminal charges,” Gwinnett’s Chief of Schools, Al Taylor, said in the release. “These threats not only disrupt teaching and learning but also incite fear and panic in our schools and community.”

Threats of school shootings can lead to confinement in a youth detention center or jail time for those 17 and older, former metro Atlanta prosecutors said. They said judges and prosecutors tend to make a big deal out of such threats and implement a zero-tolerance policy as a deterrent, particularly for young people who might not realize that an online post can be criminal.

“Most of them are juvenile cases and the kid may get probation, particularly if there’s no previous (criminal history) or other problems,” said former Gwinnett County District Attorney Danny Porter. “But there’s a chance of incarceration, even for juveniles. Kids who go on the internet and do stupid stuff usually don’t know that sometimes they’re, in fact, breaking the law.”

Attorney Chris Timmons, who served as a prosecutor in DeKalb and Cobb counties for more than 17 years, said terroristic threats can lead to misdemeanor or felony charges under Georgia law, depending on the seriousness of the threat. A threat to kill is generally a felony offense, and a threat of nonfatal violence is typically a misdemeanor. A threat to shoot up a school is arguably in felony territory, Timmons said. A juvenile court judge could be inclined to punish a threat-maker with confinement if school operations were interfered with, he said, even if there was no actual act of violence committed.

The effects of the shooting in Winder extend beyond Georgia: The superintendent in Greenville, S.C., said Friday that his district saw an increase in reported threats Thursday. That’s common after any reports of school violence nationally, Greenville County Schools Superintendent Burke Royster said.

Based on past experiences, Royster said he expects the increase in reports to taper off sometime next week.

Most of the threats reported after situations like at Apalachee don’t end up being substantiated, Royster said. While some are hoaxes, like many of the ones in Georgia over the past two days, most are made by people who genuinely believe there is a threat.

“I don’t mean to say that they are not made in good faith,” he said. “But people are hyperattentive.”

School and law enforcement officials are asking parents to talk to their children about being responsible online.

“We take each and every threat to one of our schools as real and investigate them exhaustively. It is maddening that threats like these, hoax or not, follow a horrific event like the one in Barrow County earlier this week,” Forsyth County Sheriff Ron Freeman said in a news release. “Parents, please talk with your kids and explain that mentioning shooting up a school is no joke and I will put them in jail if they do it.”

Staff writers Sara Gregory and Rosie Manins contributed to this article.