Upon controlled shutdown using shutdown(8), init(8) will attempt to run the script /etc/rc.shutdown, and then proceed to send all processes the TERM signal, and subsequently the KILL signal to any that do not terminate in a timely manner.
To power down a FreeBSD machine on architectures and systems that support power management, use shutdown -p now to turn the power off immediately. To reboot a FreeBSD system, use shutdown -r now. One must be root or a member of the operator group in order to run shutdown(8). One can also use halt(8) and reboot(8). Refer to their manual pages and to shutdown(8) for more information.
Note: Power management requires acpi(4) to be loaded as a module or staticly compiled into a custom kernel.