Android system not working, did reboot now a downloading screen

I have been getting an error message "Unfortunately, android system has stopped working" when I went to share something externally through Facebook. Today when I got that message, I rebooted my phone. Now I have a blue screen that says downloading Do not turn off target.

It's been like this for 10 minutes now.

from Android Forums at AndroidCentral.com - Ask a Question http://bit.ly/2SlxRGN
via IFTTT