There have been scores of copycat threats to schools since Ethan Crumbly allegedly opened fire on fellow students in Oxford High School in Oxford, Mich., on Dec. 1.

By Dec. 3 some 100 school districts in Michigan alone had been forced to close while police investigated threats. But the wave of threats, hoaxes and shutdowns didn’t end at the Great Lakes State’s borders. They’ve been popping up all across the country.