Killing and murder... these are social issues..
Killing can be the result of the will of the collective power.. the laws made by a group justifies it or alternately dumps it as a sinister act.. calling it murder..
This exactly is what Krishna implies in Gita..
I do not justify killing or murder as you call it but ultimately a death occurs on the intervention of too many accidental happenings.
However the collective social group has deemed it fit it to term it as attributed to the person who used the weapon and the fatal blow..
If one ponders over the entire gamut of circumstances that led to the final act, it can easily be seen that many earlier links ultimately led to the act of murder but no one had with e free will and complete control at every link that finally led to the final act of killing in physical terms.
We humans have partial blindess, partial deafness etc of the mind and spirit..
Kindly consider any particular occurrence .. it has a past and present and a future.. all of that happened or happens or will happen completely out of free thoughts and actions perpetrated by a huge multitude ..
We can shout our throats out, we can argue, and quote lawbooks or scriptures or the sayings of "wise men" to support the issue either way, but free wiill for the human had never the upper hand..
Tell me any situation, and this argument can be applied on all fours in almost all circumstances..
Lots and lots of people gather in the field and no single individual can really do anything independently