ok ,drowning in confusin here,who the hell were those ppl ???

They were doppelgangers. If you're looking for a full explanation, join the club. I think the director was going for something more ambiguous. To sort of quote Stephen King, "Some of the best horror stores are those that happen just because." That is, ones with little explanation involved.

Of course, I still thought this movie sucked, and not because of the lack of explanation. I hated the pacing.

Dopplegangers- supernatural duplicates. Google it- it's a German myth...

They were the people that live inside mirrors, doing nothing but reflecting the outside people back to them, mimicking their facial expressions. The mirror broke bringing 7 years bad luck and finally they can get out of the dark and live a little. They probably hate us and want to life our lives. However since they can only mimic facial expressions they do not actually have emotions. Next time stop making ugly faces in the mirror it really pisses them off. And when you are doing something really fun cover your mirror.