A word for acting in advance of some expected or anticipated outcome

Solution 1:

Preparatory would describe an action you do to prepare for something else.

Preventative describes an action that can stop a problem from occurring.

Preemptive describes something you do before it is necessary, often as some kind of hedge against something that could occur in the future.

Proactive means to do things before they are absolutely necessary, but I wouldn't call anything a "proactive action". I might say somebody took a "proactive step" or something of that nature.

Solution 2:

Proactive might fit here as well. Rather than be reactive (after the fact) he was proactive (taking action before the fact).