My n8's first freeze and how to hard reset it

This day is the first time my phone freezes/hangs and its kinda frustrating because I don't know what to do. Anyway the story is that I'm riding the MRT while playing games and listening to music on my phone. It was a typical day but didn't go as planned. I forgot to hide my bluetooth from all devices. So while I was playing hero of sparta someone tried sending a file via bluetooth then there it goes. I tried cancelling the transfer and then the phone freezes. Can't do nothing about it since i dont know how to turn off the phone. Can't also remove the battery to force the phone to turn off.

I only reset the phone when I came into the office. Able to research on how to hard reset it.

Hold the Power , Volume decrease, Camera shutter and Menu button simultaneously for 5-10 seconds (or until the phone turns off).