Android system not working, did reboot now a downloading screen

[Android Central Question]

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.

 

[B. Diddy]

Welcome to Android Central! Which phone? If it's a Samsung phone, force a shutdown by either pulling the battery (if possible) or pressing and holding Power and Vol Down for about 20 seconds. Then power on normally. Does it go back to Download Mode?