Updated: Just solved the problem! Here's what should you do:
(Make sure your phone is off)
Press and hold the power and volume down buttons simultaneously until Fastboot mode (image of a triangle with an exclamation point) appears.
If you see No command, press and hold the power button. While holding the power button, press the volume up button and release both.
Go to Recovery mode using the volume keys. Press the power button to make your selection.
Use the volume keys to go to Wipe data/factory reset.
Select Reboot system now once the phone is reset.