On-the-fly conf reload retrieves errors

I tried to run a “nginx -c /etc/nginx/nginx.conf” but I got:
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] still could not bind()
[Exit 1]

Then I run a fuser -k 80/tcp ; service nginx restart. I tried again with
nginx -c /etc/nginx/nginx.conf but still the same [emerg] bind() to
0.0.0.0:80 failed (98: Address already in use)

Why is this happening?

Ignore, I found the explanation