GroupAdd ???

Hello.
I have RedHat 7.1. I can add a user to an existing group OK, but how do I remove one or more users from an existing group.
1) I added a user to a group in the /etc/group file with this command. (usermod -G suzy pat)
2) How do I remove one or more users at a time from the /etc/group file.
Thanks,,,,,,,,,,Pat