A teenager at Radnor High School outside of Philadelphia, Pa. was arrested on Monday for allegedly formulating a plot to become the "first female mass murder." She had reportedly written extensive notes on how to murder her classmates and teacher before a pep rally.

New evidence collected by Human Rights Watch shows that the mass executions ISIS committed in June were on a larger scale than anyone imagined. Previously, ISIS bragged that it executed 1,700 soldiers near Tikrit around June 14. Only about 160 of those deaths were confirmed by HRW then, but now the group says 560 to 770 Iraqis were mass killed.

After capturing the Tabqa military base in northeastern Syria, ISIS militants reportedly killed at least 65 Syrian soldiers on Wednesday. According to the Syrian Observatory for Human Rights, "some were shot to death, while others were killed with knives." ISIS also bragged on Twitter about killing "about 200" government prisoners, though the Associated Press couldn't immediately verify that claim.

A laid-off California man dressed in a Santa suit opened fire on a Christmas Eve party at his in-laws' house and torched the building. Eight people died. "Naughty" doesn't begin to cover it.