Before Hiro showed up, Sylar was freaking out about potentially exploding and killing millions of people without benefitting from it. His mother’s reaction to his powers surely influenced him toward embracing the idea (he was, after all, painting the explosion in her blood while mumbling “yes, mother, I’ll be special”), but it seems the confrontation with Hiro hardened his resolve. This didn’t just set the time and place of the showdown with Peter–it altered Sylar’s attitude and behavior from that moment forward.

We know from Sylar’s M.O. and from the fact that Claire’s healing ability doesn’t work if something prevents the brain from repairing itself that powers are seated in the brain. So the Haitian can introduce static, preventing a power from operating, or he can go in surgically and remove memories.

1. Suppress other people’s powers.
2. Erase memories.

He could, of course, have absorbed those powers in the same way Peter does. We know from Claude that Peter’s not unique.