In the wake of the high school shooting in Parkland, Florida, on Valentine’s Day that took the lives of 17 students and faculty members, numerous copycat threats have put schools around the country on edge. Credible or not, some schools have gone on lockdown around America in the days following the Marjory Stoneman Douglas High School shooting thanks to students making threats on social media.

A student in South Carolina, for example, posted a picture of himself with a gun on SnapChat, threatening an imminent “round 2” at his school, Time reported.

Just two days after Nikolas Cruz opened fire at Marjory Stoneman Douglas, five schools received threats in Cincinnati alone, WLWT-5 reported. Multiple students were taken into custody due to the incidents and a middle school went into lockdown over one of the threats.

An online video purportedly threatening gun violence towards schools prompted more than 4,000 students to be released from school in Nutley, New Jersey. Superintendent Julie Glazer said it was the only decision she could make in the aftermath of the Florida shooting, the New York Times reported.

The Times also reported that a false threat at a school not far from Marjory Stoneman Douglas led to an officer shooting himself in the leg. Arrests have been made in several of these cases and others, including that of an 11-year-old girl in Florida who left a threatening note under a faculty member’s door, according to the Times.

Meanwhile, a 17-year-old boy was arrested for making a threat on social media towards a Catholic high school in Wichita, Kansas. The threat did not lead to any disruption of school events, per the Wichita Eagle. It was taken seriously, but the school was not believed to be in any danger.

Schools that have not received explicit threats have still taken precautions, such as practicing shooting drills and installing metal detectors. These kinds of copycat threats do happen after large, widely covered shootings, unfortunately. For example, a man was arrested in October after threatening a repeat of the Las Vegas shooting in which Stephen Paddock killed 58 people.

More detailed descriptions of these copycat threats against schools and more can be found here.

cruz Nikolas Cruz, 19, a former student at Marjory Stoneman Douglas High School in Parkland, Florida, where he allegedly killed 17 people, is seen on a closed circuit television screen during a bond hearing in front of Broward Judge Kim Mollica at the Broward County Courthouse on February 15, 2018 in Fort Lauderdale, Florida. Photo: Susan Stocker - Pool/Getty Images