Nexus 5 stuck on black screen Nexus 5 showing black screen

1.Can access fastboot mode

2.Cannot access recovery mode from fastboot : shows google logo and black screen (no inverted android)

3.When selecting Start from fastboot : only google logo appears and then black screen (not even the marshmallow boot animation)

Things Tried :

1.Phone was able to ring from android device manager. Tried erase from there. No response

2.Tried flashing the stock rom still no response.

What might be the issue ? Is the internal memory corrupted ?

UPDATE

The phone boots up able to hear screen shot sound but still black screen

UPDATE 2

The phone had hardware issue, the flex cable was damaged. Replaced the flex cable and phone is working again.
Since Recovery won't start up, you can clear the cache by powering off your phone and holding down Power + Volume Down for 20-30 seconds.  Then you will be able to enter recovery once you restart where you should clear the Dalvik cache and cache again.  I had the same problem and this worked for me.