New questions about guns and mental health have surged to the front of the national debate in the wake of the Marjory Stoneman Douglas school shooting.

And, like several infamous tragedies in American history, the circumstances surrounding the shooting by 19-year-old Nikolas Cruz are turning out to be just as strange as past shootings and bombings.

But the one feature that the following incidents and killers all have in common can be explored in the declassified files of the CIA under the codename Project MKUltra.

MKUltra was a covert and illegal mind control program developed by the CIA in the 1950s which explored drugs and procedures to better interrogate enemies and psychologically dominate Soviet spies during the Cold War.