You still have an instance of gunicorn running. foreman runs a daemon instance of gunicorn so if you close terminal down it will still run in the background. For this reason you should always Ctrl + C foreman before closing down terminal. There is however a way to kill the server.
Firstly you can find the id for unicorn to kill it via $ ps ax|grep unicorn
and then using the id of the gunicorn instance $ kill <id>
Alternatively you can use $ pkill gunicorn