If you would allow what is likely going to be a strange opinion...

There are many reasons to take a life that are not classically morally wrong. A life for a life is a very basic example, or killing to survive. Revenge for a lost loved one can be argued in many cases, and sometimes even insanity is a defence.

I killed my friend because I could save her honour through her death. [As well as take revenge on her betrayal, but that wasn't the best example to prove a point.] It hurts to know that I had to, but she could die without flaw, without being blamed for our collective mistakes.