Sudo Shutdown Now on Mavericks

I had read that you can "quietly shut down to single user mode" by running, within terminal:

sudo shutdown now

This sounds far preferable to having to restart the computer and hold CMND+S. However - at least in Mavericks it doesn't seem to work.

I'm getting:

shutdown: -h, -r, -s, or -k is required
usage: shutdown [-] [-h [-u] [-n] | -r [-n] | -s | -k] time [warning-message ...]

I thought that anything within square brackets was optional.

When I run it with the -k flag (which kicks all users off): sudo shutdown -k now, the output is:

Shutdown NOW!

*** FINAL System shutdown message from user@computer_name ***      
System going down IMMEDIATELY                                                  

System shutdown time has arrived
but you'll have to do it yourself                                         

Then if I try to open a new terminal:

NO LOGINS: System going down at 12:53
#my password
Login incorrect
login: 

Restarting again and terminal login is restored.

Can anyone offer some insight as to what's going on here?