our safety, terrorist attacking on site: the beginning

July 25 2015, 5 days before the incident.

One by one people are given a survey to become a D-Class. Unexpectedly, John Letter is a former terrorist. He deliberately took the bomb into his bag. The bomb will explode in 10 seconds after being held, the bomb has a sophistication where if it is held it will explode in 10 seconds. It is not known what he wants.

in site

"God help us", a D-Class who was trapped in his room because the door was jammed.

The fifth explosion caused the roof of the warehouse to collapse.

As it turned out, all of this had been planned by the scientists who scattered the bomb that finally exploded. Hundreds of classified documents were taken, and suddenly, the lights went out.

how this happen? Why they do this?