A nuclear reactor designed so small that can be placed in School Gyms. The phrase says all. It seems that shootings at schools are not longer exciting enough for the three men in the photo. They could also place dynamite under the basement and a big red button in the main entrance with a "do not push" sign. Adolescents love a defy.
Please try to be more generous in your interpretation instead of just throwing out the worst possible scenario thinkable.