That's what prosecutors do -- they prosecute criminals.
That's what members of the security services do: they neutralise risks to the security of the State. In the commie era criminals included people who distributed unauthorised newspapers, and were prosecuted for that, by now senior PiSlamic State personnel.
BTW did you ever wonder why they were turned down?
The Dear Leader Chairman Kaczynski wasn't turned down. He was judged suitable to prosecute anybody the commie leadership told him to. His brother was rejected, not him.
Besides, anyone can write a book.
This book was written in close cooperation with the Kaczynski brothers, they are quoted extensively in it.