Studi:
Obviously, the crime was not planned
From what I remember the ATCo ('Peter X' at the time)was living under a witness protection type relocation.
Kalojew hired detectives, and tracked him down with great difficulty.
He claims this was purely to show him pictures of his dead children. By some fluke he obviously (and entirely accidentally/without premeditation) happened to be armed at the time!
I'm not so sure that there is anything obvious about this not being premeditated.
Yes, tragic for all involved. However the ATCo made one of an entire series of mistakes (and if you count thoses responsible for the phone system and the Russian pilot ignoring TCAS not the biggest mistake either) - Kalojew killed a man in cold blood in front of his family.