argus913 I would recommend:
- Don't worry
- Disconnect
- Hold the power button for a long time until the device powers off
- Immediately press and hold volume-down. If the screen doesn't light after 60 seconds, continue holding volume-down while pressing and holding the power button. This should get you back into fastboot mode.
- Restart flashing
If it gets stuck in the same place, try a better cable.