This is a tricky question, in that any answer will be speculative and conjecture about angels and their reactions. In terms of the angels which became demons, they likely relish the murdering, hurting and sin. They often inspire and encourage such behaviors for who knows what reason.
In terms of the other angels, I don't know. Since the function as messengers and warriors, they often carry out their assignments without hesitation or emotional reaction. Although artists love to portray them as cute, chubby cherubs or feminine, they are actually warriors that would be a cross between the best that Sparta produced combined with Delta force or the Marine Corps. For them, completing the assignment (mission) is the priority.
Your question begs another one regarding whether or not angels can initiate or have independent thinking. If you believe that angels can, there may be some reaction to the murder, etc. If you subscribe to the mindset that they are not capable of independent action, then their reaction will focus only on how well they accomplished their assignments.
Mind you, these are my own personal speculations based on readings done and not on any kind of personal encounter or revelations.