I might kill, but ONLY ever if my actions have justification. In other words, I will never kill a person where and when another option is readily available, or when such a dire action will not cause consequences of a beneficial magnitude great enough to justify cold-blooded killing.
For example, an armed person putting the lives of many others at risk? Killing him/her might be the only way to guarantee the safety of his/her victims. But anything that CAN be resolved without lethal force SHOULD be approached in a non-lethal manner.
Though I guess that whatever we say cannot possibly take into account what we are innately capable of in stressful situations, and does not consider factors such as fear, resolve, physical capability, etc.
So, in short, yes, I would kill if I felt that it was necessary.