I just received an old Mac Mini from my friend. It was a 2014 model, sitting in a locker for a while. It got a lot of stuff so I decided to re-install Mac OS using a Bootable USB.
So, I used the disk utility to delete a partition, the Mac went freeze and rebooted. Then after 30 seconds of Apple loading logo, it went freeze again and the screen glitch like this:
I am using HDMI cable, mouse and keyboard over USB port. This didn't happen when I first booted it up but persisted after I tried to delete the disk partition.
How can I recover from this one? Thanks.
EDIT: I have tried reset PRAM and NVRAM and SMC, nothing works