Camera Light flickers an and off

I opened up my mac to do a drum practice today, and my camera flickered on - for about half a second- and back off twice. I did a little research (I'm not paranoid or anything, but I know stuff like that doesn't normally happen on a Mac), and came up with nothing. I shrugged, thought about it for a second, and got back to using my computer as normal. As I was texting my friends (from my Mac), I noticed that every other time I sent a message, the camera would do the same thing. There was an incident a couple of years back where my sister logged on to the computer, and when she did control+command+Q to lack the computer up, the camera started up, and then the computer locked. I tried logging in to a couple of other profiles, and the camera stayed on. we restarted the mac and the camera was off again and it hasn't happened since. Does anybody know why these incidents might happen? Any help would be greatly appreciated.

Thanks,

Clueless_Computer