Dec. 20, 2012 -- Schools across the country, already on edge following last week's massacre of 20 students and six adults at a Newtown, Conn., elementary school have been further unnerved following a series of copycat threats, sometimes yielding arrests and caches of deadly weapons.
From California to Connecticut, police in the past five days have arrested more than a dozen individuals in Indiana, South Carolina, Maryland and elsewhere who were plotting or threatening to attack schools.
"After high-profile incidents like the shootings at Columbine and Sandy Hook, threats go off the wall. Some of those threats turn out to be unfounded, but sometimes those incidents propel people planning legitimate threats," Ken Trump, a national school safety consultant, told ABCNews.com.
Many of these incidents turned out to be little more than young people acting out or seeking attention, but in some cases police found significant stockpiles of firearms and ammunition.
Just a few hours after the world learned what happened inside the halls at the Sandy Hook elementary school, police arrested a 60-year-old Indiana man who had allegedly threatened to "kill as many people as he could before police stopped him," according to the police report, at an elementary school in Cedar Lake, Ind.
When Von Meyer was arrested, just 1,000 feet from Jane Ball Elementary School, police confiscated from his home $100,000 worth of guns and ammunition including 47 weapons.
The school was placed on lockdown.
Meyer's case was taken by the Lake County public defender's office, but an attorney has not yet been assigned. He has been charged with seven crimes, including felonious intimidation, and an automatic "not guilty" plea was made on his behalf at a hearing on Tuesday.
Many of the suspects arrested in the wake of the Connecticut shooting were themselves school students – teenagers or young adults.
On Wednesday, in Laurel, Md., an unidentified student at Laurel High School was taken to the hospital and placed under psychiatric evaluation after school security officials found maps of the school and lists of students they believed he planned to kill.
Authorities called the evidence a "credible threat." The student, however, was not arrested or charged with a crime.
In Columbia, Tenn., police arrested Shawn Lenz, 19, who on Saturday posted to Facebook that he felt like "goin on a rampage, kinda like the school shooting were that one guy killed some teachers and a bunch of students."
He later told police that "it was stupid" to have written what he did. Lenz was arraigned Tuesday on terrorism and harassment charges and was appointed a public defender. He did not enter a plea.
A Tampa, Fla., school was put on lockdown two days in a row, Tuesday and Wednesday, after students found bullets on a school bus. Police there have made no arrests.
Despite the rash of recent threats, anecdotal data compiled by Trump's National School Safety and Security Services and analyzed by Scripps Howard found that there were approximately 120 known but thwarted plots against schools between 2000 and 2010. The list is not comprehensive and many incidents likely went unreported.
Fifty-five of those known threats -- all thwarted -- involved guns and 22 of them involved explosive devices, according to the Scripps Howard report.
"We're getting better at preventing these situations," Trump told ABC News.com.
But in that same time there were about 50 lethal school shootings, including the killing of 32 people at Virginia Tech.
"While shootings statistically may be rare, they impact a community and these kids forever," said Trump.