effects - How were Hiro's time halting scenes filmed?

In many scenes in Heroes, we witness Hiro Nakamura display his ability to stop time:

However, also in these scenes, we witness him interact with the scene, whether it be interacting with stopped objects or just to move around.

My question is how was this accomplished? Is it a simple CGI trick or a combination of that with actors/extras having to remain REALLY still?