download nexus 5 root tool kit. they have a function to flash stock and able to deal with bricked phone.
I mentioned that I downloaded nexut tool rootkit and I've tried the soft brick, boot loop option and still nothing
Did you install a custom bootloader? Because if so, if you have a bricked nexus, just delete everything off the device and reinstall a rom of your choosing. It should fix everything.
If you're able to go to fastboot mode, reflash the stock image through
+1 if its a software issue and fastboot still works, use the flashall thing in the images from https://developers.google.com/android/nexus/images if that doesn't work you're pretty screwed
He should be able to boot into Fastboot fine, if he Holds the power button and volume button down. If it's not working then it's a problem. He shouldn't need to boot into Android to install a custom bootloader.