Nothing that happens in trying circumstances can be described as “premedidated”. Did he plan it days, weeks, hours ahead? Did he plan it?
The law does not provide for any free time outs.
He obviously planned it - he looked at the crook, he went back, walked behind the counter,, retrieved another weapon and then walked back over and fired five rounds into the guy.
That was my question. Overkill, yes. And probably should be punished. Premeditated first degree murder? I doubt that the pharmacist was “plotting” to kill the SOB who tried to rob him.
In criminal law, premeditation can occur even one second before you pull the trigger.