Regulator gets hot, when current flows outside Arduino

When I close this circuit with the button, the regulator of the Arduino Nano starts getting hot and heats on, even if the button is released. The regulator only pulls 600mA after pushing the button.
Tested with multiple Nanos.
Why?

schaltkreis.png

Topic answered here: http://forum.arduino.cc/index.php?topic=563818.0

This is not about the USB source anymore. See cirquit above.