I have a 2012 Mac mini that suddenly stopped booting. It will go into a continuous loop of trying to reboot and show the following kernel panic screen. I've heard it could be either a RAM issue or motherboard failure.
The first error message you're seeing would point to a disk issue. If you have a bootable external disk and try to boot from it and you get the same message, then that would point more to a RAM or other hardware issue. Has anything changed recently on the computer?