mobile

Hello, I am mostly a beginner at android troubleshooting, having done little more than light research into recovery's, customs ROMs and such. I am attempting triage on my friends AT&T HTC One m8, which he says spontaneously shut down while he was looking at updates in the play store. It now boots only to the bootloader and while I can use the volume and power keys to select options, selecting any of the boot options, as well as recovery, simply causes it to reboot to the bootloader again. I have not attempted a factory reset yet, as my friend neglected to back up his data and would very much like to get it back, if at all possible. The phone is not rooted, and as far as I can tell, usb debugging is off. (My friend isn't really one to tinker with tech stuff) I installed the drivers for the phone on my windows 7 pc and it shows up in the device manager as "My HTC" but I have been unable to access the phone in any significant way. I did install Suqabbi's HTC One toolkit which was able to recognize that the phone was plugged in and could access the fastboot settings. I was able to trigger a reboot through the toolkit, but it only went to the bootloader again. I should also mention that it generally takes a few minutes (inconsistent) turn on the screen and go to the bootloader. This is what the bootloader screen reads:

Software status: Official
Locked
M8_UL_CA PVT SHIP S-ON
HBOOT-3.19.0.0000
RADIO-INVALID_VER_INFO
OpenDSP-INVALID_VER_INFO
OS-4.28.502.1
eMMC-boot 2048MB
Mar 20 2015,03:01:11.0

I have searched the invalid_ver_info lines and it would seem that they indicate a problem, but from what I could tell it was not a very specific one. From my research so far, I'm assuming I won't be able to fully restore the phone to its previous condition, but does anyone know of a way I can potentially rescue the data? I have used data recovery programs to get data back from corrupted and reformatted hard drives before, but I'm guessing the data in a phone is harder to get to? I also have a Macbook running OS X Mavericks (I believe) and a machine with Ubuntu Linux on it as well, if either of those operating systems might offer a solution unavailable on windows. Thank you for your help, and hopefully my friend isn't out of luck. But if so, at least then I can try to get it functional again for him.