My macair is panic now

This morning I was trying to sync the iPad on macair. Unfortunately the iTunes hanged and I thought restarting the machine will help. Who knows, it is so stubborn and refuse to shut down. I then trying to be smart and pull out the USB since sync not started. Then machine shut down immediately. Happy for a sec and continue pressed power button. A grey screen with a nice message saying "You need to restart your computer. Hold down the Power button for several seconds or press the Restart button.". Of course I followed the instruction but the same message displayed. I got frantic and immediately searched online using my iPad to look for solution. I tried safe boot, reset pram, and few more suggested resolution but none resolves my issue. ....

This screen still persists. Really hope I could resolve this issue with no cost since I already spent a fair bit in reviving it two months ago.