I have a 2013 15" MBPR and recently updated to the latest software 10.12.4. Prior to updating, everything was working fine. But now after the update.. I'll be browsing the web or using an app, then suddenly the screen will turn black, the fan will run pretty high, and then the computer will turn off. I already tried doing a NVRAM/SMC Reset, tried re-installing macOS Sierra (not a clean install). I also did boot in safe mode, in safe mode the computer doesn't turn off, but when I restart and log into my normal account it'll completely turn off at random times. I don't use any 3rd party applications, nor do I have any log in items at startup. I did run a first aid on my hard drive and that came back with no issues or bad sectors. I ran the activity monitor and don't see any unusual activity that take up a lot of CPU. What can be the issue?