This guide by user osetc will show you some commands for shutting and rebooting your FreeBSD operating system properly. They discuss commands that designate shutdown or reboot times, and sending a message to users warning them of system shutdowns. See the link below for the full set of instructions.

Shutdown Command

The shutdown utility provides an automated shutdown procedure for superusers to nicely notify users when the system is shutting down, saving them from system administrators, hackers, and gurus, who would otherwise not bother with such niceties.

How To Reboot and Shutdown System on FreeBsd