Hello' I really doubt the phone is dead. Please try the following.
- Remove the battery and press the power button for 20 seconds
- Connect the phone a live charger without the battery and press the power button for 15 seconds.
- Put the battery back while still connected to the charger.
- Wait for at least 5 minutes before turning on the phone.
If this solution does not bring back your phone then you might have a corrupted firmware. Please let us know.