You don't really need to contemplate killing someone for it to be first degree murder.

The instructions below were actual jury instructions in murder cases in Nevada, where I practiced and represented 5 men on Death Row. The instructions tell the jury that the defendant does not need to premeditate a murder for it to qualify as a first degree murder. The defendant only has to have an “instantaneous” thought of murdering the person. It is unclear how this instant thought qualifies as any kind of premeditation. Further troubling, the instructions did not define deliberation, which is an entirely separate and required element of first degree murder.

INSTRUCTION NO. 12:

Premeditation need not be for a day, an hour or even a minute.  It may be as instantaneous as successive thoughts of the mind.  For if the jury believes from the evidence that the act constituting the killing has been preceded by and has been the result of premeditation, no matter how rapidly the premeditation is followed by the act constituting the killing, it is willful, deliberate and premeditated murder.

INSTRUCTION NO. 20:  

Murder of the Second Degree is murder with malice aforethought, but without the admixture of premeditation.   All murder which is not Murder of the First Degree is Murder of the Second Degree.