[Zope] starting as a certain user

I know that I can start the Zope service as a certain user by adding the option -u user to the start script. Now when i start Zope automatically at bootup through /etc/init.d/zope_instance_xy (which calls the start script), the process cannot be stopped by the user (-u user), because there exists 1 root process beside the user processes. The pid is not owned by the user. Did I miss something? Stephan